AC current sensor, treadmill, and Wifi. Help!

Hi all, just joined the community and I think it's AWESOME. I'm trying to build a device that will detect if my treadmill is being used. What's the best way to do this? I'm thinking of making a device that the treadmill is plugged into that measures the current. If it crosses a certain predefined threshold, it will send this alert via wifi.

I'm really new and inexperienced (no engineering background whatsoever) so I would really appreciate any detailed advice.

Thanks!