They combine optical slave triggering with radio triggering, which sounds great if you are combining hot-shoe guns (which often need radio triggers) with studio lights that usually have built-in optical slaves. I sometimes work like this.
However, I use RF-602 to fire the hot-shoe guns, and they in turn fire the studio heads without any need for a separate optical trigger on the camera.
And if optical doesn't work for whatever reason, just stick another RF-602 on the studio head/s too. At twenty quid a go, it's hardly worth bothering about
You can get an RF-602 kit with a transmitter and four receivers from Flash In The Pan for £80 the lot. They work, and they are neat, small and light - why pay more?