I have made an electric rechargeable heater with a programmable 7 day timer that pre-warms the interior of your vehicle. The prototype unit works well and I think that little improvement is needed! Because I have assembled this from pre-existing products I am a little afraid of giving up to much Info, because my work could be easily copied. The working and tested unit had a cost of a little less then $300.00 US dollars. I know that I could bring the cost down considerably. The unit brings the car interior up to a comfortable temp. without having to start the engine. So it's GREEN! Also the way I have designed it, with its own rechargeable power source that automatically recharges once you drive the vehicle, there is no fear of coming out to find that your car's battery is low or dead!
Here in the Northeast of the United states where I live, this would become a Hot Item. I am comfortable in my living, but would consider manufacturing and marketing the product if I had an interested backer. Having enough seed money to buy the components used in making this in quantity, I believe it could be sold for under $200.00 and yield a profit margin of about 35%. This is not something that needs a mechanic to install. You simply sit it in your car, program the timer for the days of the week and the time of the day you want it to run, and plug the recharger into the 12 volt power port.
There is nothing like getting into a warm car on a cold winter morning, and not polluting the air while it warms up! Not to mention the trip home from your work day. Also it's nice not to have to scrape ice of the windows for the people who have to park outside "like myself at work"!