I'm guessing the Coin pre-order is why Protean sent me an email yesterday reminding me they exist: http://getprotean.com

Their Echo card is exactly the same idea, with some minor variation in implementation. It has not yet launched.

As far as the concerns voiced here (accidental button presses, etc.), Chris Bartenstein, a Protean co-founder, has addressed some of that in the comments on this TechCrunch story: http://techcrunch.com/2012/08/02/the-protean-echo-reduces-al...