App for hanging off Whatsapp after a selected time of a Videcall

[Dacdariel]

Howdy. English is not my main language, but I'll give it a try.
I'm looking for an app that could be used to hang off a videocall while using whatsapp.

The use of this app would be to have a video call, and it would end automatically after a lapse of time I previously have selected (cause I fall asleep), so my phone won't dicharge because of the videocall, but stays turned on for the alarms to work.

Thanks : )