business cards for phones lol
It'd make more sense to include a QR code and an app to scan the QR codes and pull this info later on. That way you could quickly swap cards and keep your phones in your jacket, free from digital distractions.
hehe i started this way. original name of the app was "QR-Osmosis" but even that is too much friction. The idea is you are talking at event and one of you gets pulled in another direction there is no akward "hey wait I didn't get your..." you just move on and know you have that info already.
I think streetpass used wifi, but this seems to have the same UX to it.