sorry I missed your question before! The temperature of a Smartphone is normally a bit higher than that of the room. The reason for that is that the temperature sensor is inside the phone within the battery. You might also notice that the temperature goes up when you're charging, or simply because you keep the phone in your pocket.
And yes, a temperature somewhere between 20 and 40 should be normal... generally 24 to 34 is just about right actually
Also remember you can change the graphics for the thermometer, so you don't have to use my "not-so-professional" looking one
Still, it's quite a nifty thing to show your mates if you want to show what a Smartphone can do