Just on the security side of it I would not make a system like this. You may have no ill intentions but the ability to see if someone is home or not with out their knowing they are being looked for and checked on is open to abuse.
The real question is how they would react if they found out after you had already been doing it...
Depending how many there are, you could always propose to do it, and hook it into a device that is centrally located or in a common area, and therefore available for the convenience of all?
thats what i was thinking about, having a smart mirror in the common area that has that info, but i would have it on my phone well before that was finished
Well when there's a party make sure to have all of them enough drunk to pass away, take them to a pirate clinic and put a GPS tracker in them. This way you'll know everywhere they go pretty easly.
Jokes aside I may be considered a cynical bastard but I would do it. To make things more fair I would talk to them and give them access to the site too if they accept to do be "tracked".