Ah crap, why do things always break just after Christmas?

I started working out tonight and my hear rate monitors watch just stopped working. I assume it just means the battery is dead, but I am not sure — I took the back off and it is not an ordinary watch battery so I am not sure where you get those or how much they cost. Maybe it’s the sensor that’s gone rather than the watch? Maybe something else entirely is wrong.

Either way, ugh, I rely on that thing — especially as I was about to start a new regime!