Sen.se has a small smart temperature monitor called ThermoPeanut (it does kind of resemble a peanut) that can be stuck just about anywhere to keep track of the area’s temperatures. Inside of the fridge is one example, if you’re particularly concerned about the temp getting too high; you could stick one in your bedroom or the basement, behind yourELECTRONICS in the entertainment system, or even in the car. Temperature data both past and present can then be accessed from your mobile device.
The ThermoPeanut itself is quite small and sticks onto a surface; the sensor connects to your smartphone over Bluetooth Smart and then uses that connection to send over temperature data. The image below shows the related SensePeanut mobile app and the various ways the temperature data is presented (more pics in the gallery below).