Turn Signal Switch & Brake Light Questions

This is an old post, but let me ask a question, as I've been wondering about this too.
I believe that the front turn signals are completely independent from the brake, parking, and headlamp circuits - so might the easy way be to simply splice into those wires to feed the new back lamps?

I'm facing sort of the opposite challenge. Take a look at my picture to the left - I've replaced the parking/turn-signal lamps with a single LED ring. What I'd like to do is have them act as parking lamps under most conditions, but have them flash as turn signals when necessary. (I could always use a relay on each side, set up such that the turn indicator 'signal' turns the relay OFF, so it would flash when the indicators are operating. (I think it would flash with a pattern opposite the rears, but that should be OK.)

Any bright ideas out there? (Get it?)