Osmos has been around for a little while, but it might appeal to some on the forum. It consists of moving a "mote" around the screen, absorbing smaller motes. Doesn't seem like much but it can be very trippy especially with the new age music on headphones and running the game at slow speed. I find that if I don't try to achieve anything, it has an almost zen garden effect. Very calming. And there's no illegal substances involved.
I've got the PC demo running on my 24 inch monitor and the real app on my iPad. I'm zoning out here, man!
There's videos on youtube and the game's site is:
http://www.hemispheregames.com/osmos/