Theres a App that monitors just about everything on your phone and its free. It called: SystemPanel Lite. I currenty use it. Once you download it go into it. Tap on Menu, Monitor, and Scroll all the was down the screen and you should see what your looking for. Hope that helps. Oh by the way My Droid is stock and running 2.1 and the current battery temperature is: 95.0F Degrees. That was during an Idle. The highest I seen it go was about 105.0F Degrees.
I too run System Panel and It is great for monitoring the Droid X. When I was just charging it in my office the battery temp was 109.4F It has been over 114F in the car doing navigation near the AC vent and out of direct sunlight. Seemed quite hot to me so I shut it down to let it cool off.
I looked into the same and was told the battery is rated for 60 degree celcius max and the cpu is 70 degrees...I work in a kitchen phone in my back pocket streaming a baseballl game and the max I saw was 54 celcius...I put the phone in front of the ac for a minute and changed kernals now I average 48 to 50 while doing the same thing and I have no issues...at home and everywhere else I range from 25 degrees to 43