This device looks like it will allow you to shoot a series of HDR brackets exactly like you want. It also, allows you to shoot time lapse sequences. Although, normal remotes like the Canon TC-80N3 do time lapse just fine. The real strength of this device is HDR brackets in a far more flexible way than any of the in-camera bracketing features.
Don't get me wrong, you don't have to have this device to shoot great HDR. Dan Achatz, who I consider one of the kings of HDR says he only ever shoots 3 bracket series, two stops apart which almost every camera can do with built-in features. So, while the Promote is a really cool piece of gear it's not essential. At $300 it's also a bit pricey, but it does way more than any other remote that I've seen.