2. Social Media
One of the worst parts of GTA IV was the whole friendship thing. Having characters calling you constantly when you just wanted to play the game was annoying, and whilst some of the activities were fun, having to do them regularly made them a bit of a chore after a while. Instead of having friends contact you, why not let you contact them? Social media sites like Twitter and Facebook have changed the way we socialise, so it would make sense to include something similar in the modern setting of GTA V. Having a site (accessible on your phone thanks to the aforementioned internet capability) could let you see a post or status from a friend saying something like I'd love to shoot some hoops right now. Then you could like or comment (from a range of pre-set responses) saying something like Me too, see you down the courts in an hour. Then a marker would appear on the map to start the activity. This means you wont get hassled with phone calls constantly and it incorporates the real-world phenomenon of social media into the game. It could even let you see posts from characters you meet on certain missions (like a celebrity perhaps) who might reference something your character has done.