David, I'd suggest to use physics or biology as targets.

I mean, try to build a bridge between your research area and the applications... which ultimately could turn into a technological or daily application.

Examples:

• Differential geometry -> General relativity (gravitation) -> Fine corrections in GPS devices.

• Lineal Algebra -> Quantum mechanics -> Transistors -> Computer and cell phones

• Chaos theory -> Critical points -> improvement of Weather predictions

• Dynamical systems -> (Population modelling ...)

• Path integrals -> Financial market

And so on...

Good luck with the seminar... and enjoy it!!!

P.D.: Include graphics, short videos or simulations, cartoons... I'd also suggest you to watch the film Freakonomics, could help you.