The Polar FT40 HR monitor watch is a mid-range offering from Polar USA, the premium manufacturer of heart rate monitor watches.
This HRM sports watch comes with the WearLink chest strap monitor, which is worn around the chest to monitor your heart rate (HR) with ECG (ElectroCardioGram) accuracy. The WearLink is machine-washable, and has a user-replaceable battery. The soft textile strap is also impregnated with anti-bacterial agents. The WearLink transmitter transmits with a coded signal, which minimizes interference with other monitors and electronic devices, and is especially useful if you want to use the FT40 in a gym class.
This Polar FT40 has a large display area which simultaneously displays your current HR, both in numbers and graphically as a pointer sliding across a bar, as well as the duration of the current exercise session. It also displays what the major effect of your current exercise is, either “Fat Burn” when the rate of your heart at 60-70% of your maximum heart rate (MHR), or “Fitness” when the rate is above 70% of your MHR. There is a thin dashed line on the HR bar that graphically depicts 
where the 70% MHR threshold is, so that you can adjust your exercise intensity. You can also set your own target HR zones, either before the exercise session, or on-the-fly during exercise with a few simple button pushes (the Polar ZoneLock feature). The ZoneLock feature is especially useful if your desired exercise intensity changes often, or if you reach your desired exercise intensity and target HR by feel, and once you get there, you would like to maintain that intensity for a certain amount of time. Once your target zone has been set, the FT40 both visually displays the target zone on the heart rate bar, and gives you an audible alarm on how close you are to the edges of the target zone. The FT40 can also be configured to display the calories burnt in the current exercise session, which is very helpful if you’re trying to burn up a certain amount of calories (note that you must manually update your weight weekly for this feature to be accurate).
At the end of the exercise session, the FT40 HRM watch saves all the data it has collected, and you can view the data 
from the past 50 exercise sessions, or view a weekly summary of your exercise. With the Polar FlowLink accessory (available at additional charge), you can transfer the data from this HRM watch to your PC or Mac and onto the Polar website, if you choose to do so, so that you can perform your own custom analysis.
As a watch, the polar FT40 comes with a date and weekday indicator, a backlight, an alarm and stopwatch, a user-replaceable battery, and is water-resistant down to 30m. The FT40 comes in 3 colors, black, beige and green, and 2 strap designs, a thick strap for men, and a thinner strap with floral patterns for women.
In summary, the polar FT40 is a very useful heart rate monitor watch for monitoring your exercise intensity, and its ZoneLock feature is especially for those who would like to adjust their physical training intensity on-the-fly.