The D-Link DCH-S161 is roughly a 2.7" square white box that is about 1.2" thick. It uses (2) readily available AA batteries which are included to get you started, and houses a built in 90dB alarm siren. The unit comes with a sensor probe with integral cable that is about 6 feet long. It is wall mountable and is operable through the mydlink app, Google Assistant and IFTTT. Surprisingly Alexa is not included on this device.