also check out hello messenger, i just got it the other day and am currently testing it. this app goes the pin route like the BB. but instead of being hardware based the pin is randomly generated for each user. this app doesnt allow you to send vid/vcard/gps in chats but does support groups. it also has a "buzz" feature, just like the bbm "ping". theres a free ad supported version and a paid ad free version. there are also blackberry and android versions coming, hopefully you can chat across all platforms. facebook integration too, check it out.
http://www.hellomessenger.com/