It's pretty much what the title says...this is a mapping tool for Google Chrome, showing you locations of crimes committed in the UK. The data is originated from the UK Police though it must be noted that due to legal requirements the latest results are usually two months before the actual date.
ADDITION:
UK Crime map is not availbale in Chrome Store anymore due to the changes in Web App publishing system and it is not feasible to me to put any additional effort to maintain this application.