This works very well indeed. You can pick up baby's heart beat very easily. If baby is lying with its back to your front there is a strong pickup. Otherwise, you may have to poke the doppler into the side, top or bottom of your lump to try to get a good sound, but I've never been unable to find a heartbeat somewhere, even if it's a bit faint due to awkward positioning. If you leave the doppler on the heartbeat for a short while, the heartbeats per minute show up on the LCD screen and that's very reassuring.
One set of in-ear phones is supplied but there are two sockets for earphones so both parents can listen together if you have an extra set of earphones to hand. The lead that links the unit to a recording device is supplied. It's easily linked to your laptop or PC.
I assume the only difference between this doppler and the cheaper one is the LCD screen. If you're not bothered about seeing the heartrate and want to go for the cheaper option, I'm sure it will work just as well. You can easily distinguish between baby's heartbeat and your own pulse. Baby's is very quick (bangbangbangbang) and yours is quite slow (bangpausebangpausebangpause)...a strange way of explaining it, but I'm sure you'll understand when you hear it.
A nice sized bottle of gel is supplied and you don't need much at all to get going!