No, it just gets hot. I know there are some apps that can monitor certain temps as well.

 

Actually just this last week i was working on my car and left the phone on the drivers seat in the sun. I went to check something on it and it was hotter than it's ever been thanks to the fact that it was under direct sunlight. It had a message on the screen saying that it turned off radios and was too hot or something to that effect.

 

Mine has done this before too if it's in direct sunlight for a long time. That was on stock Froyo though, haven't seen it happen on CM7 (but I've also been much more careful about letting it get that hot again.)

 

Ah, I guess that mine has never gotten that hot, or maybe it doesn't do that on CM7/9? I have felt the device get really hot a few times with no warning.

 

Here are some tips for preventing overheating more simply,
Turn of the Mobile Data in the settings menu, This alone will prevent overheating throughout the entire day (unless of course you use apps that require the processor to work) not only will this prevent heating up but it will save a ton of battery life. About 2 days of use. Or airplane mode, The only downside to airplane is not being able to text. But your battery should last for even longer.

 

There's a free app called battery booster. You can configure it so that it displays the temperature in the status bar. It can also beep when its overheating if you set that up.