https://www.kickstarter.com/projects/2012099678/minijam-studio-portable-music-machines
Looks kinda fun. I won’t be buying though.
Indeed, they will fit in your pockets as promised, as long as them pockets are large enough and you have 5 available! 
Kidding aside, these minijams look like a lot of fun but I wouldn’t say I’m tempted to buy. If and when I want to make music on the go, I always have my iPad Mini and iPhone with me (not in my pockets though :)) and they take care of the job nicely. Yet I’m sure there is a strong market out there for this type of gadgets. Nearly a month left until the end of the campaign and over 90 % of the target fund has already been met. The devs must be happy I guess.
(Unintended double post, my bad, sorry! Note to the site admins: why is it not possible to delete posts?