PartyWareiPhone is a project mainly written in OBJECTIVE-C and C, it's free.
PartyWare for iPhone
Project requires:
Junction for iPhone (http://github.com/OpenJunction/iPhoneJunction)
GData (http://code.google.com/apis/gdata/)
ASIHTTPRequest (http://allseeing-i.com/ASIHTTPRequest/)
ZXing (http://code.google.com/p/zxing/)