Is there a way I can setup family and friends phones to act as presence sensors without full smarthings access?
SmartThings has an official integration with the life360 service that will do this.
However, they would probably have to be very good friends, since there are some tracking possibilities with life 360 that many people would find intrusive.
And alternative with more privacy would be to set up a Wi-Fi connection tracker, assuming that you are willing to give them your Wi-Fi password. (You could set up a guest network on your Wi-Fi for just this purpose.) You’ll find further discussion of that in the following thread. That requires more technical expertise, though.
Some router brands like the Google OnHub or the Asus make setting up a Wi-Fi presence system easier than other brands.
The third option would be to use an I Beacon. Then each person has to have a receiving station app on their phone that would detect the beacon and do something to alert smartthings to its presence. This is definitely doable, but the set up is more complex than life 360. You would only need one I beacon for the house, not one for each person, but there is an additional device cost.