The Fluval 2-in-1 Digital Aquarium Thermometer displays both aquarium water and ambient room temperatures. Innovative wireless technology allows you to mount the thermometer to the outside of the aquarium glass and position it without the need for probes or wires.
Simply remove the adhesive backing and affix it so that the sensor on the back of the unit rests against the glass (below the water line)
Key Features :

2-in-1: Measures water & room temperature accurately within 1C / 2F
Wireless technology: no probes or messy wires Large LCD display simultaneously shows aquarium and ambient room temperatures.
0C / 0 F temperature selection
Large, easy-to-read LCD Display
For fresh and saltwater aquariums

Also available :

11195, Fluval Digital Aquarium Thermometer with suction cup,