(Pocket-lint) - Smartphone makers are realising they need to come up with new ways to excite buyers, and one of their strategies seems to be coming up with new form factors such as foldables, or in this case, crazy tall phones.

Andy Rubin - the tech executive who co-created the T-Mobile Sidekick, then later co-founded Android but left Google after being accused of sexual misconduct, and ultimately went on to create Essential Phone - has teased a mystery device on Twitter. It appears to be a colourful, very long phone with a unique user interface showing card-like apps and widget-like on-screen buttons. 

At the same time, the phone looks quite small to hold. It has a large button and volume toggles on the right side, as well as a fingerprint sensor on the back below a single primary camera. But the real stand-out detail is those metallic finishes that seem to shift colours.

Essential, the maker of Essential Phone, has also confirmed it's been working on a new device to "reframe your perspective on mobile". It's now in early testing, with the Essential team now using it "outside the lab". The company plans to share more "in the near future".

Essential also tweeted images of the new phone, officially calling it Project Gem: 

Bloomberg first claimed in 2018 that Essential was working on a new phone controlled mostly through voice commands, and Essential suggested in December that it was indeed working on a follow-up to the first Essential Phone. Leaked code uncovered by XDA-Developers indicates the Gem activates its voice assistant with a finger tap on the back, and it mentions a “fingerprint walkie talkie” mode.

The phone also appears to run Android and possibly has a Qualcomm Snapdragon 730 processor.

Writing by Maggie Tillman.