Most reliable, accurate HRM.

Accurate for heart beats normally means a chest strap but other methods are improving all the time.

But heartbeats don't convert into calories, that "accuracy" is hugely affected by your activity (many activities are completely unsuitable for using HR as the basis of an estimate) and your personal exercise HR which is very variable.
Also remember that the estimates tend to be gross calories not net calories which becomes quite significant for longer durations.

I used the FT7 which is a nicer watch (in a 1980's retro way...) than the FT4 but similar very limited functionality.
When that broke upgraded to the FT60 which is far more modern and sophisticated and you can calibrate it to yourself quite successfully if you have an alternative more accurate way to estimate calories. But that also broke. I use a Garmin cycling specific computer these days.

First thing to consider is do you actually want to know your HR?
If not and calories are the metric you really want then maybe use an app like Strava (not the MapMy suite of apps though as that seems to give wildly exaggerated numbers) or using a running calculator (making the assumption your "route" was a run)?

The DCRainmaker site has comprehensive review of HRMs and other tech.

Rocketts81 wrote: »

Any suggestions for one that won't bankrupt me. Sick and tired of my Polar FT4, which despite fresh batteries, packed in on mile six of my route yesterday and lost all data! Also research states they over calculate calories burned up to 12%. Routinely I subtract 10% in the hope of a more accurate result... the FT4 is about £70 - any ideas for a better option?

regards, David

Accurate for what? Accurate in measurement, to be honest there's not much in it. Accurate in extrapolating other data? Depends what you want to extrapolate and what activities you do.