We had a new heat pump installed in February, and they installed an Ecobee 5. It came with one remote sensor we put in the bedroom. You can get more sensors for about $40 each if you have a larger house.
It's one of those devices that "just works" -- it sort of figures out your usual schedule over time, or you can tweak and twiddle if you prefer. We like having a temperature readout, and it also senses humidity.
So far, everything has been seamless. The Ecobee works great, the app works fine, etc. It's an Alexa voice-enabled device, which is a feature you may or may not consider a positive. I have not set up the voice activated stuff and probably won't.
At first, it was a little too aggressive in seeking savings, letting the house drop to 64 degrees at night from an "occupied" setpoint of 70 degrees. I mean, yeah, saving energy and money is nice but that was a little extreme for us and I changed the settings.