Nike+ sportwatch GPS for counting Calories

Options
I bought a nike watch so i could count how many calories i would burn indoors at the gym on the cross trainer, HIIT classes and weights.

It doesnt work and the shop said it would!! it only works on the tredmill (when my feet are moving) and even then it was out by 100 calories.

I also want to see how much i burn through out the day to.

Should i get rid of it and buy a different watch or am i doing something wrong with it?? (i have the pod in my shoe aswell)