Yes a Polar one is ideal, especially if you're planning on using it in the gym, then the cardio machines are equiped to link in with the Polar heart rate monitor, so your heartrate will show up on the machine's display. Most gyms use Life Fitness machines and these are Polar enabled.
There are many different specs of Polar monitors, from basic to the more elaborate ones. They mostly usually come with a Digital type watch, so your heartrate etc will be displayed there.