The M2 Black will give you easy real-time monitoring of heart rate and calories and works with most gym cardio-equipment.

Chronograph

Stopwatch

Heart Rate
Calories: In real time
HR: in real time
HR zones
Memory Capacity: 1 log and 4 week totals in unit history menu

Heart Rate Belts
Suunto Comfort Belt, Analog Coded (Compatible Not Included)
Suunto Dual Comfort Belt, Analog Coded & ANT Coded (Included)

Other
Dot-matrix display
Menu-based user interface
Operating temperature: -20C - +60C/-5F - +140F
Selectable metric/imperial units
Storage temperature: -30C - +60C/-22F - +140F
Water resistance: 30 m / 100 ft
Weight Max. 40 g

Power
Low battery warning
User replaceable battery

Special
Button lock
Languages: Menu in 9 languages (EN, DE, FR, ES, IT, FI, SV, NL, PT)

Training and Exercise Guidance
Automatically switches between 3 HR zones
Recovery time suggestion after exercise: FALSE

Watch
12/24h
Calendar clock
Daily alarms: 1