thermometer rigging

Hello,
I just bought an aftermarket thermometer for my 97 tahoe. just looking for some ideas on where i should mount the sensor. the directions say to mount it outside the vehicle. I am thinking door jam but i am open to any thoughts. i would like to get the most accurate reading.

Also, this unit came with a cigarette plug but i would like to hard wire it so it only has power when the key is on. where would be the best place to get power to this thing.

thanks!

jo