Bahahaha :lmao:
To subject: There is no definite answer to your questions. Some people just get on the bike and go, some meet up and plan a route, some meet up and take random turns and see where they end up.
In fact, I have done all three of those last weekend. It all depends on what kind of mood you're in.
Calculating lean angle? Lame. You'd only be able to do that if you mounted the phone to the bike AND if you trusted the gyro in the phone, which I think is not as accurate as some seem to believe.
Communicate to friends over bluetooth? So you mean I need to buy a mic for my helmet and basically have a really long phone call with one friend at the time, and when I end up out of my local area it's long distance charges for me? Scala (and similar devices) are already available for that and will outlast iPhone's battery if you were to try and make it do something similar.
Seeing people's location is easy. All major smartphones have Google Maps installed and there's this neat little feature called Latitude. It works really well and all you need is to add your friends to your Latitude contacts.
Went camping in Gatineau with a few people couple summers ago and I got lost in the mountain bike trails and ended up on a road that I didn't know.
My buddy hopped into my truck and was able to come get me when I sent him a text saying "hey im lost. come get me please".
If you REALLY want to impress me, write a script that goes through all the Google Street View within a 150km radius of GTA and make it record where all these signs are. Then make a website that has a pin to show where all those signs are located, and then I can design myself some nice routes for when I am joyriding.