[reg_dunlop]

Reminds me of https://diewithme.online/ which I just learned about.

Not exactly the same as your idea, but definitely in the same vein of "only available under a certain condition"

[xp84]

This is most definitely an invitation to abuse your phone’s battery, but at the same time I absolutely love this idea. It’s hilarious to imagine someone eagerly awaiting the chance to log onto the site as the battery dips from 8, to 7, to 6. “Just a couple more minutes…”