(Pocket-lint) - If you remember the Psion 5, 5mx or 7, you'll know that those early personal organisers had great keyboards.

Although British firm Psion was too early for the mobile device revolution over the last 10 years, it produced some well-loved devices that have stood long in the memory.

And those memories are why a different company - Planet Computers - has chosen to produce a device that puts a 2018 stamp on the Psion - an Android mobile device that features a decent mobile keyboard.

It's designed by Martin Riddiford, the man who designed the original keyboard on the Psion Series 5.

There are two versions of the Planet Computers Gemini PDA - a Wi-Fi-only version for £499 and a Wi-Fi and 4G version for £599.

If you're scoffing at the Wi-Fi-only version then we understand, but it actually could make some sense - if you have a phone contract already that you can hotspot and tether the device to, then why bother with another SIM?

While it's naturally possible to use the Gemini as a phone, we suspect it will be a second device for many. If it is used for calling, we suspect a Bluetooth headset would be preferable as it looks rather ridiculous held up to the ear.

If we consider that the main use for this device is mobile working and its key USP as being comfortable typing, then there are two different rivals.

Firstly, Bluetooth keyboards that you can tether to your existing phone and secondly, tablets with keyboard docks. Of course, what's best for you is down to personal preference - the Gemini certainly has compactness on its side.

171.4 x 79.25 x 15.1mm

Clamshell design with full mechanical keyboard

5.9-inch display

The name Gemini is based on the two main elements of the device that make up the clamshell design. On top there is a 5.9-inch, 2160 x 1080 pixel (403ppi) display and on the bottom a full mechanical keyboard (it works really rather well).

Measuring 171.4 x 79.25 x 15.1mm this isn't a small device by any stretch of the imagination, but you could slip it into a jacket pocket and take it with you on your travels. It is, however, just over 300g so is quite a bit more weighty than many smartphones.

The outside is clad in a dark grey metal (Planet Computers calls it Space Grey) with a fairly utilitarian design only interrupted by two USB-C ports, a voice activation button, and a 3.5mm headphone socket.

Strangely for a 2018 device there is no outward-facing camera to take photos with. Planet say you can add a camera, but it's an £40 optional extra. Things like the SIM slot and microSD card slot are hidden behind the case (coincidentally, it's eSIM-ready).

The lack of no screen on the outside of the device does mean you can't see who is calling. To combat this there is a row of coloured LED lights that you can program to change colour depending on who is calling. If it's your partner it can glow red, while it could be green for the office for example. It's still not an ideal solution we feel.

MediaTek deca-core processor, 4GB RAM, 64GB storage (plus microSD slot)

4G, 802.11c Wi-Fi, GPS, Bluetooth, eSIM support

4,220mAh battery

The Gemini PDA runs Android on a MediaTek deca-core processor with 4GB of RAM and comes with 64GB of storage, which is expandable via microSD.

There are the usual array of connectivity options, 4G, Wi-Fi, GPS, Bluetooth, and eSIM support. There are also integrated stereo speakers for listening to music or watching TV and two USB-C sockets for charging and also for outputting to HDMI so you can connect the Gemini to a screen and treat it like a computer (you can buy a USB-C to HDMI from Planet although of course others are available).

The Gemini features a 4,220mAh battery and we must say the battery life has been fairly impressive, lasting much more than a day.

Lightly modified Android Nougat

Android Oreo coming soon

Psion inspired apps and dock

The device runs Planet's own version of Android which is lightly modified for this unique device with some apps that are Psion-inspired such as Agenda. While our review device has been running the ageing Android Nougat, Planet have apparently been testing and Android Oreo-based version. There's also a dual boot option to run Linux should you want to do that.

Planet has clearly tried to keep things as simple as possible and not stamp its influence all over Android. However, there is an app dock that apes how the Psion used to do things.Just like in iOS on the iPad, the dock is there to help you get to your favourite apps quickly.

Full QWERTY experience

Better than many flimsy Bluetooth keyboards

A handful of manufacturers have launched devices with keyboards in recent years, and while it was once the input method of choice for devices from BlackBerry for example, many companies like Samsung, LG, Apple, and Sony all moved to an onscreen keyboard experience many years ago.

The argument here is that on-screen keyboards are OK and while all Android devices will support a Bluetooth keyboard, they often aren't very pocketable. Of course, there's a big dollop of nostalgia here too. This isn't going to be a laptop replacement, but as an email machine and for typing documents it's great.

The sacrifice for the Planet Gemini is clearly in the size of the device itself. Adding a keyboard more than doubles the thickness of the phone taking it into Nokia Communicator territory. But as you'd expect, the keyboard here is very good to use for typing documents and emails and almost identical to the one found on the original Psion.

You just have to be very nimble, as the keyboard real estate is 100mm narrower than a full-sized keyboard. It does take a bit of getting used to even if the all-important key spring/travel is just right. On the downside, it doesn't allow for any error when striking keys, so it's hard to use on a train for example.

Verdict There's one thing for sure - this isn't going to be a laptop replacement. But it's not designed to be; it's a fast and easy-to-use PDA for those who used to love the original Psion as well as those who want an Android-based device with a built-in keyboard as a tablet alternative. It's difficult to get away from the feeling that this is a niche product, but if you really do type a lot of documents and emails but don't want to carry around a laptop then it's a definite option.

It might be a bit long in the tooth, but the iPad mini is still hanging in there. You'll need to add an external keyboard to get Gemini-like functionality and it's not as good as the new standard iPad, but it's a compact option for those who want a bit more than a smartphone when on the go. Apple iPad mini 4 review: Compact without compromise

Writing by Stuart Miles and Dan Grabham.