Most tools estimate a shop's revenue from its traffic. SKUmio counts instead. We read a competitor's published stock levels every 2 to 12 hours; when stock drops from 84 to 79, five units sold. Multiply by that day's price and you have revenue, per product and per variant. You also see which size sold out first, when their restocks arrive, and the ads running on those same days. No plugin, no access to their admin panel. The check is free and takes 60 seconds; monitoring starts at $0.30 a day.