Can switches like this also detect usage, like current flowing? It might be a fun and healthy twist to plug a walking pad/treadmill into a smart plug and then either make it so brainrot websites are only viewable when the treadmill is being used or make a small app that tracks the time the treadmill is used and then only allows that amount of time on brainrot websites.

Yes, a lot of them do. There are some $5 plugs I use that monitor current and work great:

https://www.aliexpress.com/item/1005005729080838.html

The price varies a lot between listings, I think the cheapest I got them was $20 for 4 or so.

I've deployed countless Sonoff S31[0] which are easily hackable and have current monitoring capabilies

[0]https://sonoff.tech/product/smart-plugs/s31-s31lite/