Thermometer HD is great application which measure the temperature outside or in your room! Result is shown on beautiful drawn thermometer!
Let me explain how this thermometer works.
When selecting 'Outside' option application will try to download actual temperature for your position (longitude and latitude) - it is very accurate. Be sure that internet connection is available while choosing this option.
When selecting 'Battery' option application will give temperature of the sensor placed on battery inside the phone. It can measure temperature of the room, but it is still inaccurate as the battery usually has bigger temperature than temperature of the air.
When clicking 'Menu' button on the phone you can select 'Settings' - there you can change background and customize the Thermometer this way!