03.2025 update:
Had it installed for a few years. It used to work ok on booking .com, suggesting switching to another country or to the mobile app for a lower price, but now it doesn't show those lower prices any more...

Well, it really works!

I'm glad I discovered Ratepunk! It helps me to check the same hotel price at many booking sites in one window. I don't have to do it manually just to ensure I'm not overpaying for a hotel.

Just installed and found a Hilton 50eur cheaper on Agoda, than on booking. Thanks, Ratepunk!