I often use booking.com to book hotels with free cancellation, sometimes I cancel and rebook at a cheaper price because the price gets lower closer to the date.
I found the site http://heyitscheaper.com that claims to check the price of my hotel periodically and send me an email if it gets cheaper. It doesn't ask for any credit card or address etc. but I'd still like to know if there are any risks involved that I'm missing as it seems like a good service otherwise?
UPDATE: So I didn't hear anything from them for a week, then they sent me an email that my hotel was cheaper so I just cancelled and re-booked at the cheaper price ( benefits of free cancellation !) So I ended up saving 30$ with no hidden fees as advertised - highly recommend this site.