Fun App needed - measure active times of motion sensors

I've been writing a rule when it occurred to me that a useful app would fit the bill.
I have a number of motion sensors of differing brands. It would be great if I could run an app that gave back a report by taking the active to not active timer of each of my sensors for review.
Obviously it's not a daily use thing - more of an informational task.

Right now, I've a rule that has a button trigger - it then waits for a device to go motion active, logs the time, then sets a trigger to log the time when it goes deactive. subtract the two and you get your 'motion active length' value for a specific device.
I haven't figured out how to store seconds (don't need mills) - so currently my rule only shows minutes - so work to be done. but anyway - if anyone is bored....!

The information you're collecting is also present in the Event and State details for the device. So easy enough to ask for the motion events and subtract the inactive date/time from the active....

I expect you could append the events you are detecting in the rules to a local file, then read the file back in as part of a html file hosted locally on the HE hub, presenting that in an iFrame. No app needed.

But obviously an app would be more user-friendly to pass on to others and to configure.