iPhone 4 heating up / draining battery

When I got off of work today I went to find my phone in my purse, and felt something warm in the pocket. It was my iPhone 4, hot to the touch. It also had 9% battery life remaining, when that morning it was 87% and only used for about 20 min. during the day. There wasn't many apps running at the time, and no new notifications other than a few emails. Is this a serious issue?

was it on and running?

Mine has never done that, and battery life should be longer, maybe take it to apple?

My Iphone 4 had similar problem. It happens if you activate all services , wifi, bluetooth on your phone. Turn off all the notifications keeping only your 3g service on . The problem will be solved. This will also increase your battery life.