my wife and i have used these on and off for 5ish years.
any 5$ pedometer will "count" your steps all it is, is just a weighted ball that counts a step when it moves
then we go into the fitbit, i've had 2 fitbits, the latest one the flex is awesome. they give you one of those livestrong type bands and the fitbit fits in there, it's waterproof, and charge lasts 1 weekish. the flex is great b/c you don't have to "sync" to your computer no more, it auto syncs to your droid or iphone via bluetooth.
THIS IS IMPORTANT, cuz otherwise it's a pain in the ass to sync to your pc every other day. you also plug in a fitbit receiver and it'll autosync when near. these fitbit can talk to popular fitness apps like myfitnesspal, you can show your friends or join groups to see how much you've walked.
the device has no buttons, just tap it physically and it'll show you 1 to 5 lights, when you reach 5 lights thats your goal for the day. (you can adjust it)
there''s a bunch of other stuff too, but does it count calories? no, it just counts steps, and then by doing psuedo fake science some apps can sorta think how many calories you've burned (since you also enter in your weight/age...)
what it does is keep track of what you do. 2000 steps one day? wow you're thinking you're a lazy ass...
when i had my dog i would avg 12k to 15k steps daily, cuz i would walk my dog for that long (and regular movement)
when i lost my dog, i really didn't have a purpose to "Just walk" and my activity went down to a scary 2k (fitbit can't do treadmills well, funky readings)
we used to have the gowearfit, or also known as the bodybugg or the thing that all the biggest losers strap on their arm (this is where it got popular), it needs constant skin contact because this does measure calories burnt, through sensing skin ****. it wasn't water proof and you needed a yearly subscription in order to basically decode the info.
i could never do the sleep monitor cuz for most of them you have to "tell it" your gonna sleep, for me, i sleep when i sleep, so nah.
just ask questions and i'll answer.