Couple of questions about vivofit and Endomondo apps

Portly_Priest_no_more

Hi. I received a vivofit wrist pedometer (etc.) today, and I'm already connecting my myfitnesspal account to my endomondo account (or vice versa) and it brings up a couple of questions.

How does a wrist based pedometer actually count steps? Is it by arm movement? I ask because for my serious "I'm doing this to lose weight" walks, I use a walking stick. It cuts my arm movements on one arm in half, effectively, and I wonder if this would mess up the step count.

The second question has to do with linked accounts: would I be right in assuming that I should only have vivofit (Garmin) OR Endomondo linked to myfitnesspal? I'm thinking that if Endomondo uploads the walking data to mfp, and the vivofit uploads my all day activity (including the steps of the walk), wouldn't that duplicate the data, and thus double up my available consumable calories?

Looking for some good advice here, folks, and thank you in advance. And to our American mfp folk, happy memorial day.