Hi there,
I would really love to help you with this! I'm a product manager by profession and have extensive experience writing product and feature specifications and working with visual and interaction designers. I was a senior product manager at TomTom for 2 years then at eBay for 3, so I have first hand experience in the automotive industry, and with eBay/Gumtree, both of which I believe to be relevant to your project.
My approach to writing product descriptions is first and foremost to understand who the target audience is (consumers, businesses), and then to figure out what about the product would appeal most to them. An example from your landing page, "BT Sync" wont' mean much to your average consumer, however, "...the ability to play your favourite songs straight from your smartphone" is awesome; where do I buy one! Sell the benefits, not the actual features.
On the design topic, I work with designers on a daily basis. My approach to a collaboration is to involve them early, and to ensure a complete understanding of the key messages we're trying to get across. I find the best way to get good results is to work using a fast, iterative approach with regular communication and feedback.
To summarise, I really believe I could add value and I'd love to work with you and your team on this great project. If you need any further information please let me know?
Best,
Camilla.