Hmmm, they do make blinking LED's. It wouldn't be very hard at all to figure out something that had a strip of them that mount to the top of the hatch. The wiring would be easy, just a resistor and the led. The powe draw would be minimal enough you could tap in to the existing brake lighting probably with no problems. Of course they would flash all the time, but still it would get attention.
I might mention I have a similar fear that you do. If you check the post about led tail lights I'm still considering doing it. I am currently waiting for 300 more led's to be shipped from hong kong right now. But if I go for it and buy two new tail lights to modify I'm going to make tail lights that will have 200, 5mm led's a piece. 100 of which will be just for the brake lights! I don't want to promise I'm doing this, but I'm committed to the first step. If this goes through, at 6,000mcd a piece from the red led's they should hurt to look at. This is not going to be a cheap mod, but people will know I'm stopping NOW!
I might mention I have a similar fear that you do. If you check the post about led tail lights I'm still considering doing it. I am currently waiting for 300 more led's to be shipped from hong kong right now. But if I go for it and buy two new tail lights to modify I'm going to make tail lights that will have 200, 5mm led's a piece. 100 of which will be just for the brake lights! I don't want to promise I'm doing this, but I'm committed to the first step. If this goes through, at 6,000mcd a piece from the red led's they should hurt to look at. This is not going to be a cheap mod, but people will know I'm stopping NOW!