It’s basically a MIDI controller built on a pad, largely on a grid – much like a stringed instrument’s notes are, except providing expression and note control and you move your fingers around. There’re demos of using it to play slide guitar, expressive saxophone, violin – I can imagine it being workable for drums but it’d probably be underusing a lot of the LinnStrument’s power for expression.
And it’s based on the Arduino – and the software is open source, at that! (Or the site claims – I didn’t see a reference offhand to the source repository. Geert told me it’s going to be available when the instrument is available, which makes sense.)
At $1500, it’s not cheap (nor has it been released yet, as of September 9, 2014) but it looks really nice – it’s a little like the Eigenharp in providing a different and unique control surface, while being a little less intimidating for people like me.