I have a
Beacon 2 (no, it doesn't flash, but is a FINE product),
and
Hyperlites to satisfy my flashing pleasures.
The Hyperlites come with a loop-wire that if left alone, the LEDs will flash constantly while the brakes are applied.
If you cut the loop, the LED's will flash about 5 times (I forget the number) and then go steady until you release the brake. If I want to repeat the flash sequence, I release the brake and reapply it.
They are two small pods of 8 LEDs each. I fastened one to each of the turn signal bodies.
That guy in the OP really knows his stuff, though!