Moments people watch for
A few of the situations that started this whole thing.
Restock alerts
Limited drops sell out in minutes. Watch the product page and get pinged the second "Sold out" turns into "Add to cart."
Ticket drops
The original reason signalp.ing exists. Festival and concert tickets go fast. Boost the checkout page right before doors open.
Price tracking
Waiting for something expensive to drop. Set a price watch and stop checking the listing every day yourself.
Listings
Apartments, job postings, appointment slots. Anything that gets snapped up the moment it appears.