Pros: Good sound quality
Cons: Not wireless?
This kit comes with replacement earpads that have built-in wired speakers (with another small wire that connects tham and tucks up inside the back of your helmet). You just pull out the normal earpads and pop these in their place, and you're done.
There is a standard 1/8" stereo miniplug jack on the left earpad; you can use any audio cable to connect it to any device with a normal headphone jack. The kit includes a male-male audio cable that has an inline volume control and mute switch, and that can clip onto your jacket for easy exterior access. Nowadays you can get fancy wireless audio kits, but this works with any device, and you don't have to deal with Bluetooth sync hassles, dead batteries, etc.
Sound quality is fairly good; they don't sound quite as good as my Koss Sportapros (which, to be fair, are one of the best lightweight "sport" headphones available.) But they're way better than really crappy headphones. They are 'open' enough to hear your surroundings if you keep the audio at a low enough level. When they are off or muted they don't seem any worse than normal helmet earpads in terms of my ability to hear.
If you want to rock out to some sick tunes while still protecting your brain, this kit and a compatible Giro helmet will do the trick.