Most of the agregator websites like priceline, hotels.com, orbitz, expedia, etc. will display hotel rates but will not tell you if you need to book your room now or later for the best price. Similar to Kayak, that predicts air fares, TheSuitest predicts hotel room rates.
All you have to do is enter your destination city, click the prices and availability button and TheSuitest will show you a graph of both availability and price predictions. Enter specific dates for predictions for a particular hotel.
Along with the room price predictions, the website also gives graphs of various amenities. Clicking on, say, the square footage of a room will give you all the options of area in that city. And depending on the size of room you want you can refine your search.