It's always rewarding to see how far, how fast, or what distance you've been biking. Cyclometers tell you all of this and so much more, in the iteration of bike computers out there right now. Add on: heart rate, GPS functionality, power meter measurement, altimeter, temperature, and more, and you've got a cyclometer that can just about do it all. Granted, an all-in-one bicycle cycometer with that many features is going to run a pretty penny - we're talking $200+ for most well-known brand name cyclometers with GPS and the ability to download and analyze your data later. Ask any cyclist who is charting power, elevation gain, etc., and they'll tell you it's worth it. That's not to say a basic cyclometer isn't desirable - they certainly are! For $40 or less, you can get a great cyclometer that gives you all the basic data you need: distance, time, speed, cadence, time of day, and you can store data by laps. And remember, through roughly 2000, that was the extent of most cyclometers. When you add in the ability to measure and store heart rate data, unit prices jump to usually $75 or more. Cyclists of every kind - from Tour de France professional riders to weekend recreational riders - benefit from the precision, ease of use, and reliability of the best cyclometers. You need to weigh the features, functions, and specifications of each cyclometer you might buy to determine what you need for your bike riding training and racing. And now, you can use your smart phone as a cyclometer in many cases.Clark Kent jumps in a phone booth and becomes Superman - your iPhone or iPod Touch can transform with the right app into a cyclometer. Some of these apps are even free! Then there are cases and integrated devices you can use with your phone; one is the iBike Dash + Power. It's a weatherproof holder that mounts quickly and securely to your bike handlebars for a clear view of all the data. It will protect your iPhone from the elements, and it houses all of the custom electronics that allow you to later track trip and workout info on your computer at home. There are sensors placed on your bike that signal the iBike app. It is user-configurable, so you can see your trip and graphical interval data in real-time as you're working out. The iBike Dash + Power is compatible with all Ant+ sensors, of which you have your choice on the open market. There are 4 types of batteries that are often used for cyclometers. Alkaline - some older devices like the Cateye Astrale use penlight-type cell batteries. Lithium - most modern cycle computers require lithium cells. They have a very long usage charge, suited well for a low-drain application just like a cyclecomputer. Lithium batteries are fairly common, and therefore cheap, and they offer a consistent voltage output during their entire usable duration. Then there is mercury and silver oxide, neither of which you'll frequently find in cyclometers. So determine what functions you are looking for in your cycle computer: speed, cadence, altitude, power measurement, heartrate, and so, and make your choice based on the features you need.