Fess up, you like to drive fast don't you? Perhaps fast enough to break the speed limit from time to time? Naughty.Helping you try to avoid speeding tickets and points on your licence, TomTom has launched the TomTom Speed Cameras app, that helps you stick to the speed limit if the road signs aren't being that helpful - and, more importantly, detect speed cameras ahead in the road.Speed cameras save lives but they are also the bane of motorist's lives and, some might think, are there solely to raise cash for the police force's Christmas ball. Either way, there is nothing worse than a car in front braking suddenly because the driver hasn't noticed the camera and was going too fast.In drives the TomTom Speed Camera app that sits on your iPhone for you to plonk on your dashboard, giving you a clear indication as to what speed you are doing, what the speed limit of the road is, and whether you are breaking the law.In addition to letting you keep an eye on your speed, the app will also tell you when a speed camera is coming up. It will also detect mobile cameras so you won't get caught out.The app tracks and displays fixed cameras, mobile cameras, average speed checks and red light cameras, and you can select a 10, 15, or 20-second audio warning depending on how much time you think you need to hit the brakes.When there is a speed camera coming up on the road ahead the app's graphics change, giving you a visual cue as to what is coming, and as long as you've got an eye on the phone it's very easy to spot.The app also lets you report a camera at the touch of a button if it isn't on the system already and you've spotted it.In practice and the app does what it says it will do: keeps an eye on your speed and warns of oncoming cameras so you've got plenty of time to plan accordingly rather than just slamming on the breaks.We tested it on an iPhone 3GS, although the app will work on the iPhone 4 and the iPhone 4S. As you can see from our pictures we had our phone in the TomTom iPhone GPS cradle, although this isn't necessary.To get the full benefit of the app you will need to join TomTom's subscription service, at an introductory price of \u00a31.49 a month, increasing to \u00a33.99 in the future. If you opt against paying this you'll just get the speed data and not the speed camera warnings.Also worth noting is that to ensure you have the most up-to-date information about the latest locations of speed cameras around the country you need to be connected. We tried the app with and without a connection and didn't notice any difference, however. We also weren't able to confirm how much data the app uses and how often the app needs to update itself.If you drive a lot, don't know the whereabouts of the speed cameras and are fed up of being caught, \u00a31.49 is justifiable; at \u00a33.99 we aren't so sure.We aren't sure because we don't know who this app is for exactly, aside from TomTom trying to eek out some extra milage on the services that it already offers.The app works, but we've yet to find any of the people we asked who think it is a must. Those who don't know where they are going will use a sat nav with the speed camera data already in it, and those who do will surely know where the speed cameras are.Also, unless you have a docking cradle for powering the phone, the constant need for a connection (GPS and data) means your battery life will be affected. The iPhone battery isn't great as it is, so abusing it in this way probably won't be ideal for many.What do you think? Would you use the app? Let us know in the comments below.