[Q] Switch on hotspot when Wi-Fi unavailable topic

I have scoured around everywhere and tried a number of hotspot control apps to no avail.
I'd like to set my droid to turn on it's hotspot facility when it's out of range of a usable wi-fi.
This in order that my second droid can latch onto that portable hotspot wi-fi when on the go.
The second droid only uses wi-fi data.
Look forward to the responses.