Core stability is a critical component of driver fitness, and TRX straps are a seriously effective way (i.e. hardcore!) of developing it. A strong core stops the body twisting and contorting under high cornering loads, which allows the driver's arms and legs to remain relaxed and fluid rather than having to brace the body against the car/seat/pedals. This is critical in retaining absolute prescision and finesse on the steering wheel and pedals throughout the entire cornering process - from brake point to exit.
Here's the brilliant Pete Webster of Driver Performance demonstrating a few key moves. Rep each one out - SLOWLY and controlled with rock solid stability - for 30secs (or as long as you can last). Build up the time from there.
If you don't have these straps in your gym, you can buy them from Amazon, which is well worth doing as they're perfect to whack in your suitcase and use when away travelling. If you need a trainer, call Pete - I can't recommend him highly enough.