If you're not concerned about emulating speed and distance and don't care about cadence, your cheapest route would be a Wahoo TICKR ($49.99), or any other Bluetooth heart rate sensor, and their free Wahoo Fitness app for you cell phone. The app should give you the data that you are looking for. If not, there are many other cycling apps that will do what you are asking and most of them have a free, but limited function, edition. Since you are going to do this on a trainer, it really shouldn't matter that much as to whether the data collector is on your wrist, a table next to you or on the handlebars of the bike. If at a later date, you decide to go with the Polar M400, you don't need to buy their HRM sensor as the TICKR will work with it.