Mobile phones and sim card standards.

Is there a standard I have to confom to if I want to use mobile services on a mobile device (i.e. O2, virgin, Orange ect) if its not for commercial purposes (fun ) where can I find the specs needed to read simcards and communicate with the mobile companys network and are there any 'legal' issues? If so, is there a better way of providing internet access and communication between devices?

hmm, are you talking about a network between devices? And something like cables just wouldnt work, and as such you have considered using phones as a 'medium' between the two devices??

http://www.elektor-electronics.co.uk/Default.aspx?tabid=28&year=-1&month=-1&art=50650&group=<<%20empty%20>>&PN=On&SearchText=mobile%20phone is a project that lets you play with a SIM card not attached to a commercial service