JustBook is a new hotel booking app, available from your local app store (App Store, Android Market, Blackberry). It is a very niche product – every day, at noon, it lists 3 (and only 3) hotels in each city it covers, available only for that same evening. All are discounted (in theory).
JustBook appears to be German-run, since it has substantial coverage across German cities, as well as Austria and Switzerland. Of more relevance, it is well represented in the UK with Birmingham, Edinburgh, Glasgow, London, Manchester and Oxford covered.
Outside these places, it is currently patchy. Amsterdam, Brussels, Budapest, Dublin and Prague are covered but no other cities in those countries.
JustBook is doing a promo with The Independent at the moment. If you download the app and enter Indy as the promotional code when registering, you will receive €20 of credit against a future booking. This is of greatest use outside London, obviously.
I did a quick comparison on Monday evening of some of the offerings. The Indigo in Glasgow was £96 vs £135 on priorityclub.com. The Radisson Blu in Birmingham was £111 vs but just £103 on the hotels own site! The Macdonald Holyrood in Edinburgh was £107 vs £170 direct. Dukes Hotel in London was £276 vs £281 direct.
There are savings to be had, then, but you need to do your homework. The €20 credit means you should save OK, though, at least on your first booking.