Ah, ooops I didn't remember that detail, thanks @Taifun for highlighting..
So please @Gwen_Ceylon forget that suggestion (that kind of watchdog).
In effect I do my BT watchdog as follows:
every 30 seconds (or even more, with a clock) I do a handshake: i.e. the App sends one character (typically I send a '$' 
) and waits for the echo from the Server (or the opposite, it is irrelevant to the scope). No echo means that the communication has ceased, therefore I popup a warning and I retry a new connection.
In @ABG 's FAQ you can find this:
The rest of my previous post (i.e. the initial clock probably too early) remains valid. Please give it a sight.