Pausing timer in mytimeout

[cflurin]

It's a similar use case we discussed here:

Cumulative running time

I am looking for suggestions on a node, or way to capture cumulative running time of equipment. For example: a machine runs for 2 hrs, then is down for 20 minutes, then starts again for 3 hrs, so the cumulative time is currently 5 hrs. I would also like to access this value at anytime say 5 hrs 4 minutes, 5 minutes, 6 minutes etc... thanks