Yeah, this is for people who have foolishly abandoned their land line service along with their indestructible telephone set, 99.99999999999999% network reliability and clear transmission not subject to satellite lag that went along with it.
Except for my cordless/answering machine phone, all phones in my house are vintage rotaries, and those in key parts of the house have their ringers enabled.
This doorbell idea wouldn't work for me unless I picked a particular phone with a distinctive ring to work with it. I see no reason why a touch-tone phone wouldn't work on this system. The ringer mechanism on those is no different from their rotary contemporaries.
What would be interesting to know is whether this gadget will work with a stand-alone chime ringer. I have one of those installed as well. I suppose that would defeat the purpose, but it would sound more like a real doorbell.