My recommendation is the:
Giga T Pro II 2.4GHz Wireless Timer Remote for Canon Cameras
Noob, there are various answers here, but it really depends on what you ACTUALLY need.
- simply a 'wireless shutter release' - for 5DmkIII??? OR
- a 'wireless FLASH' trigger for a certain external flash???
I have the Giga T Pro Wireless Timer Remote for Canon, which works great on both my 7D and my Canon 350D (it comes shipped with 2 different cables, 1 for most 'older' Canon DSLRs and a three pin for some of the 'newer' ones!) I'm very happy with that.
It allows a good working range, batteries have not yet needed replacing, and I like the flexibility of it being an intervalometer (eg that I can do time-lapse and control from inside, while my camera is outdoors)
Plus, it's a simple 'self-timer' / portrait help too. I'm not 100% sure if this will work on the 5DmkIII - but someone else (or google or the Hahnel or Canon websites should tell you!)
If it's option 2) - as I don't have a Canon 5DmkIII, I might have different requirements. (The 7D can control remote flash, wirelessly by it's own flash, etc).