Meet the Party Squasher: a smart occupancy sensor that counts the number of mobile devices within a range and alerts you if the number goes above your limit. It sends you notifications via SMS or e-mail. You can use the app to manage multiple properties. The Party Squasher simply attaches to your router and counts the number of mobile devices.
This device could prove useful for Airbnb, HomeAway, VRBO and short-term rental services in general. Sets you back under $160 at this time.[where to find it]