Thanks HK. I hadn't thought of BPD/Nxh refusing to use it, very good reason to keep it free!
I have looked at
www.2houses.com which is now free. I guess it can't hurt to use free and see what it is like and if he responds well to it.
We use GMAIL now, but I am always worried about it being too personal. Other apps keep it about the kids which I like and you can share pictures, school reports, care details like dr info etc and shared expenses. You can request money and change for visits and it tracks the sending, delivery, and response, or lack of.
Actually, he probably won't use it. Told me he can't drop the kids at my house because I have a video security system. People who have nothing to hide hide nothing... .