Space requirements
The HM-1 is a small sensor that is assembled into either a medium or deep frame. The sensor itself is 1.7"x1.7"x0.5" (4.2cmx4.2cmx1.3cm) in size and can be removed and placed inside the hive between frames hung by an extended paper clip.
Smartphone requirement
More importantly, the smartphone you use to download the data from the HM-5 must be either:
an iPhone 7 or newer (such as an iPhone 8 or iPhone X)
an Android supporting Android 6 operating system or newer
If you are looking for an Android that supports both requirements above, one inexpensive, approx $100 option, is the Motorola X4 (the 4 stands for 4th generation). See the attached manual. There is no need to purchase a phone plan with this phone. Simply buy it without a phone plan and use it as a WiFi device only.
Note: Solutionbee no longer recommends the LG Phoenix 2.
Moto x4