The GPS only Apple Watch can do Everything the cellular model can do as long as your iPhone is nearby, where nearby is somewhere in the same 3-4 bedroom home (assuming typical wood frame construction).
Keep in mind that for all intents and purposes the cellular carrier now has to track 2 cellular devices, even if it is just sharing the iPhone's phone number. That Apple Watch is putting more work load on their network as each tower in range of the Apple Watch now needs to report to the switching gear that the Apple Watch can be found at this location. You Apple Watch costs the cellular company when it is connected to their network.
Now whether it is costing $10 per month is a totally different question.