Presence does require both devices to be connected to the Internet through WiFi or a high-speed cellular connection. Wifi is not required to use Presence, many users are connecting with cellular data systems. The challenge is there are many cellular data systems and they are not all the same.
- 4G, LTE we have shown excellent results.
- E (Edge, 2.5G) can have some challenges.
- 3G is in between, if you have a lot of bars it should be fine.
- 4G usually is sufficient.
This is a great temporary option if you are away from home, camping, RV'ing, or other places where you don't have a WIFI channel to access. Cellular can get expensive however so that is why many folks use Wifi.