$3 car cigarette lighter mounted in the compartment behind backrest.
Connected all the time. It charges my cell phone and accepts Battery Tender Jr. And those of you who can't get enough excitement from the physical risks associated with riding, it can light your cigs too!
BTW, I charge the phone only when parked. Phone batt. is small enough and I don't want any voltage spikes or reg/rec failure to kill my phone. If the regulator fries itself at 5000rpm, I would probably need that cell phone to call for help! When parked, I know nothing is moving and it's between 12.5 and 13V. Much less worries to plug it in while I set up the tent and cook my dinner next to my companion. If I am not camping, I can usually find a wall outlet for charging the phone.
GPS is a different story though... Gotta have it plugged in while traveling. Do car/bike GPS units come with a surge protector? It would make sense to have one: We protect our PC's with it after all.
1985 VN700, 30,500mi and counting