I have a polar FT7M which will do for the basics and is decent quality at the same time.
Will monitor your heart rate, and you can input your weight and it'll tell you the calories burnt. Comes with a belt strap thing and the sensor, the computer "docking station" to monitor/evaluate long term data is extra.
Available for ~70 EUR.
Really happy with it so far, and every time I go over 1k calories/session I'm extra happy.

Don't get the black/red one though, as the backlight is a bit weak and numbers aren't too easy to read depending on the lighting...