Basic heart rate monitor, and the cheapest you will find from a mainstream shop that is all over the UK. You could be using it before going to the gym/jogging tonight.
The Kinetik Medical Heart Rate Monitor is designed to help you keep a check on your heart rate during physical activities.
How to use:
Step 1) Enter data into watch, Fix transmitter strap to chest
Step 2) Exercise and monitor heart rate
Heart rate monitor watch
2 CR2032 batteries