Nephalem Rift timer

Greetings,

I am looking for something along these lines:

- When you enter a Nephalem Rift, a timer starts.
- When you close the rift, the timer stops.

That should be done automatically and the timer should be displayed on screen (probably an overlay).

The reason I am looking for this is that I am trying to get the Torment X Nephalem Rift cleared under 2 minutes Conquest and I always forget to start a timer.

Is there any tool that already does that?

Otherwise, would it be possible for someone to create such a tool?

Thanks a lot for your time and help.