That stuff is complete crap. A bunch of guys in my dept started buying those and telling me that I'm an idiot because I "overpay" for Whelen.
A few months later, every single installation that they've done for themselves and other people they've convinced to get them have partially stopped working.
One of them asked me to do his installation... I agreed to help him do it so he didn't set his car on fire. The best part was when it came to the flasher - it resets the pattern every time you turn it off... his solution? Tape a piece of a broken poker chip to the "B" button, leave the power button on all the time, and put it under his hood and wired it to a switch.
I tried to convince him to do otherwise but it didn't work. I basically told him it's your car, make sure you tell people when they ask who installed it that you did it that way because you're cheap and wouldn't listen to me telling you not to.