I keep my phone, computer, GPS, iPod, alarm clock, flash light, camera, movie camera, weather warning radio, calculator, CD library (350 CDs), cookbooks, address book, survival guide, knot tying guide, first aid guide, several novels, newspapers, board games, compass, small tv, theodolite and of course 3 bike computers all inside my iPhone and my iPhone inside my Mophie case and I keep that inside my handle bar bag along with my back up charging system (TekCharge MP1580) and spare AA batteries. 4 alkaline and 4 NMH. I also carry a small telephoto lens / small tripod that can become a full size tripod with attaching my tent poles for the iPhone. The bar bag is padded and I have a padded case for the phone and always a couple zip lock bags just in case. For a year or so I was keen on mounting the phone to the bars to be viewed and in a weather proof case but as time went on I felt it safer and better to stop and get it out when needed.
Bar bag is small and attaches with hooks (easy on and off) has a carry strap. It always comes with me off the bike.