Sorry if I am being thick, but I don't understand why you brought tilt switches into the conversation.
If you are talking about modding a current rear light, that might explain it, but I don't see how a tilt switch would work. Although having said that, there ARE accelerometer based brake lights out there - check out
this thread that I started 2 years ago.
I have thought about making a brake light mod to a dynamo before, but always stumbled at the same hurdle - how to actuate it. In the end, I decided the simplest and easiest method would be either micro-switches to bypass a limiting resistor or potentiometers to vary the brightness even more depending on how harsh the braking was. The problem I found was that the switches would have to be on both brakes to be effective, and single lever dual action brakes are rare. So I gave up.