We did have a recent thread about fitbits, I'll see if I can find it.
I used a regular pedometer for years that I clipped to my waistband or pocket. It's a nice option if you want to go low effort and just track your steps, and you don't want to wear something on your wrist. (They're also more accurate than wrist based trackers, if that matters to you.) And they're pretty inexpensive now; you should be able to get a nice digital Omron for less than fifty bucks.
With the Fitbit brand specifically, they have a few models out now. I've had the Charge for a year and a half now. I basically wear it as a watch. It tracks workouts, steps, sleep, and stairs climbed. The Charge HR is the same size but also has a HR tracking ability.
My Charge is starting to peel off the plastic housing in one area, so I literally just bought a Fitbit Alta, their new wrist model, the other day but haven't really worn it yet. It's narrower, and has the ability to display texts as well as notify you when your phone rings if you have a compatible smartphone. It also has the ability to change the wristband, unlike the Charge, and they sell different colors and styles.
There's also the Fitbit Flex, which doesn't have a numerical display, just some kind of dots to show how much you've walked. And they have some smaller clip style trackers that can be clipped onto a waistband or worn in a pocket. I think Janet said she has one of those, the Fitbit One.
