The usual disclosure: we make Sayph, so we’re a participant here, not a referee. HMD – the company behind modern Nokia phones – has done something notable with the Fuse: it’s a real smartphone with an AI content filter called HarmBlock+ built in, designed to block sexual imagery in any app, even end-to-end encrypted ones. HMD describes it as a phone that “grows with your kids”. That’s an accurate description, and it’s also exactly where the two phones part ways. Since we first wrote this, a security researcher has published serious findings about the Fuse and UK sales have been paused; we cover that below.
In brief
The HMD Fuse is a full Android smartphone with staged freedoms. It ships locked down – calls, texts, approved contacts – and parents progressively unlock capabilities (apps by approval, then more) as the child grows, with HarmBlock+ designed to filter explicit content throughout. In the UK it was sold through Vodafone and Three on contract, or £498 SIM-free; at the time of writing, sales are paused.
Sayph is a deliberately simple phone that doesn’t grow into a smartphone. No app store, no browser, no social media – permanently, for everyone. You buy the handset outright, put any UK SIM in it, and the line you set on day one is still the line two years later. When your child is truly ready for a smartphone, that’s a new decision you make on your terms, not a slider that’s been creeping open since Christmas.
An update on the Fuse’s security (October 2026)
Since we first wrote this guide, an independent security researcher, Paul Moore, has published findings on the Fuse and its HarmBlock+ system. He says he spent seven months reporting them privately to HMD and to Xplora, the company that runs the HarmBlock+ parent app, before going public. Among other things, he reports that:
- a flaw in the parent-account system let someone else take over a parent’s account, see the child’s live location, manage their apps and switch off the phone’s protections remotely;
- in his tests, turning the phone on its side made an image the filter had blocked reappear around 70% of the time;
- a child could remove the protections with a factory reset, and the filter doesn’t scan 433 approved apps, including ChatGPT and Wikipedia.
Moore reports that the parent service was offline from 8 July to 10 September 2026. VodafoneThree has taken the Fuse off its website and, in a statement Moore quotes, says it has paused sales while the issues are reviewed; at the time of writing, HMD’s own UK store lists the Fuse as out of stock. We haven’t seen a public technical response from HMD or from SafeToNet, which makes HarmBlock, so we can’t tell you which of these issues have since been fixed. Moore’s full write-up has the detail.
We take no pleasure in this. HMD set out to tackle a real harm, and the idea behind HarmBlock is a good one. But it shows the limit of any filter: it has to catch harmful content every time, on every screen, and keep its own systems secure while it does. Sayph takes the other route. The browser, app store and social apps that most of that content arrives through aren’t on the phone, so there’s nothing to filter. No phone is tamper-proof, ours included, but there’s far less to get wrong.
Side by side
| Sayph | HMD Fuse | |
|---|---|---|
| How you buy | £189 one-off, SIM-free (Sayph Phone 4G, a Samsung Galaxy A16 4G; the 5G model, a Galaxy A17 5G, is £199) | £498 SIM-free, or on contract via Vodafone or Three (from roughly £23–£33/month plus ~£30 upfront, typically over 36 months). Sales paused at the time of writing |
| Subscription | £4.99/mo Sayph Space, cancel anytime | Airtime contract required; parental app included, carrier extras vary |
| Typical 2-year cost | ~£309 + your own SIM (~£2–3/mo) | ~£498 + SIM if bought outright; ~£580–£820 on contract |
| SIM | Any UK network, swap anytime | Any network if bought SIM-free; tied to your carrier on contract |
| App store | None – cannot be added by anyone | Apps available with parental approval; expands as child grows |
| Social media | Not possible | Possible later, at parents’ discretion, as freedoms are staged open |
| Explicit-content protection | Risky surfaces absent by design | HarmBlock+ AI designed to block sexual imagery across all apps; a researcher has reported ways round it (see above) |
| Web browser | None | Managed/staged access |
| Contacts | Parent-approved only | Parent-controlled contact permissions |
| Message oversight | Every message visible in Sayph Space for up to 30 days, plus AI summaries; never seen by staff | Screen time, app limits, location via HarmBlock+ app |
| Location | Real-time via parent portal | Real-time via guardian app |
| Philosophy | Hold the simple stage for longer | Grow toward a full smartphone inside one device |
| Recognition | MadeForMums Gold 2026; reviewed by Smartphone Free Childhood | Strong early tech-press reviews; serious security findings published in 2026 |
Fuse pricing as it stood in July 2026, before sales were paused. Treat the numbers as indicative and check HMD, Vodafone or Three for current availability.
Where the HMD Fuse is the better choice
- Explicit imagery is your number-one fear – and you want your child to have the apps it usually arrives through. HarmBlock+ is aimed squarely at that specific harm and is meant to keep working whatever apps are added later, though read the security findings above before you rely on it. (To be clear, this isn’t a gap on Sayph: the usual routes to explicit imagery – a browser, social media, WhatsApp, file sharing – aren’t on the phone at all. The Fuse’s edge is filtering those routes if you choose to allow them.)
- Your child is older, or has already had a full smartphone, but you realise they need some protection. The Fuse gives you one device that starts locked and opens up as they grow.
- You prefer a monthly contract that bundles handset and airtime into one bill through a mainstream carrier’s support.
Where Sayph is the better choice
- You don’t want the ratchet. A phone designed to grow will grow – that’s the point of it, and children know it. Every capability that can be unlocked becomes a negotiation. On Sayph there is nothing to unlock, which is why the pestering stops.
- Your concern is broader than explicit content. HarmBlock targets one harm: sexual imagery. It isn’t designed to address group-chat pressure, addictive design, notifications, or the always-on social world. If those are what worry you, filtering the screen doesn’t answer it; simplifying the phone does.
- You want out of the contract model. No 36-month commitment, no carrier lock-in, no credit check on a child’s phone. £189 once, any SIM, cancel the portal subscription whenever you like – the phone keeps working.
- Total cost matters. Over two years the Fuse route typically costs roughly twice as much, and at the end of it you’re mid-contract on a device designed to become the thing you were delaying.
How to decide
We’d suggest asking where you want to be in two years. If the answer is “my child on a managed smartphone, freedoms half-open, one device the whole way” – that’s the Fuse. It’s built for that journey, though we’d wait until it’s back on sale and HMD has answered the security findings. If the answer is “my child still on a simple phone, and the smartphone decision still entirely in my hands” – that’s Sayph. One phone is an escalator; the other is a landing.
Still comparing the whole market? Our complete guide to phones for kids maps every option by age and type, our guide to every HMD Fuse alternative compared covers the full field, and our objective buying guide weighs each route on its merits.
Frequently asked questions
How much does the HMD Fuse cost in the UK?
£498 SIM-free, or on contract via Vodafone and Three from roughly £23–£33 per month plus around £30 upfront depending on tariff and data (checked July 2026). Sales have since been paused while security issues are reviewed, so check HMD and the networks for current availability. Sayph, for comparison, is £189 outright plus £4.99/month, with any UK SIM.
Does Sayph have anything like HarmBlock?
Sayph takes a different route to the same worry. HarmBlock filters explicit imagery inside apps; Sayph doesn’t carry the apps that imagery arrives through – no browser, no app store, no social media, and picture messaging only with contacts you’ve expressly approved.
Can the HMD Fuse become a normal smartphone?
By design, yes – parents progressively unlock apps and capabilities as the child grows, with HarmBlock continuing to filter explicit content. Sayph deliberately never becomes a smartphone; when your child is ready for one, you choose it then.
Which is harder for a child to get around?
No phone is tamper-proof. HarmBlock runs on the device, but security researcher Paul Moore has reported several ways round it, including turning the phone on its side and a factory reset. Sayph’s restrictions are the operating system itself, with no settings to find and switch off. The bigger difference is what each is protecting against – imagery on the Fuse, the whole app-and-social world on Sayph.
Sayph is £189 with free UK delivery, plus £4.99/month for the Sayph Space parent portal. See how Sayph works or order today.
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