My treadmill is nine years old, and it's still going strong. However, the battery in the Polar monitor chest strap that came with it croaked a few months ago, and it's one of the old models where the battery isn't replaceable.
I had a Polar HRM chest strap/wrist display combination back when I was a skinny cardio git in the early 1990s, and enjoyed heart rate training way back when. And since cardio health has become important to me, I decided to shop around for a replacement strap.
http://www.polar.com/us-en/products/acc ... ate_sensor
The Polar H7 uses GymLink to communicate with a broad variety of fitness equipment brands. Since I travel a lot, and use treadmills other than my own, this seemed handy.
More importantly, it incorporates Bluetooth to interface with fitness apps on iPhone, most notably being Polar's own Polar Beat. It's free to download and use the basic features, but it's like $6 to upgrade to the full version, which gets you record-keeping, analysis of your training sessions, and a "share" on social media function (if you're into that sort of thing).
Physically, the unit has replaceable Li-Ion batteries, and the monitor unsnaps from the elastic chest strap so that you can wash it. VERY important feature.
If you intend to be a cardio bunny or if you just want to more methodical in your training, it's a great piece of equipment.
Tell us if you found a gem or a piece of shit, and who peddled it