Yeh I don't want to pay that for a doorbell. I tell you why though.
I have a normal Intercom type thing outside, and it's getting a bit annoying now with kids or people looking for food randomly ringing that thing, late at night, or early morning..
So all I want, is to see if I can just find a solution, where the notifications comes through to my phone, which will also be annoying, but at least at night I can mute my phone. The RF solution bell Saba'a posted might just work, if I get a Sonoff bridge.