This review was amended in January 2013 order to make clear the distinction between the Polar T31 transmitter and the separately available Polar wristband displays.
The T31 is the standard Polar chest band heart rate transmitter. It is also available in a package with Polar wrist band heart rate displays such as the Polar F4, F6, F7 etc.
If you work out in a gym equipped with modern treadmills, cross trainers, steppers, cycle exercisers etc you will find that the machines are all capable of picking up and displaying the heart-rate signals transmitted by the T31. So if you only work out in the gym using modern exercise machines (e.g. Technogym) just buy the T31 at less than half the price of the full transmitter and monitor package. If you later decide to use it for running, cycling or swimming, just add a Polar wrist band monitor.
The T31 is good value for money, in my opinion. Just ensure that the two conductive strips (look like carbon fibre) on the inner face are slightly damp before starting: once you get into the calorie burning zone your perspiration will keep them that way!