"Android tablet bluetooth-interface for sPOD."
Toggle switches are cheap, simple and reliable. More importantly, switches are trusted, technology isn't. Others have already expressed concerns about what happens when the tablet is broken. Obviously, tablets are far more useful than any toggle switch, and this should be your focus if you intend to market your idea in the overlanding community (in addition to GPS, geocaching, editing photos, blogging, performing conversions, etc., you can now operate all of your 12V accessories with this new product). Your idea adds functionality to a platform that many people are already using.
Just think how fun it would be to change the labels/icons of switches, change the order in which they are arranged, or even change the colors of the icons to help identify them easier -blue for the ARB fridge, white for lights, red for winch controls, etc. By providing complete control over their 12V gadgets, you would be providing people with a unique experience and far more flexibility than would be available otherwise.
With the diverse offerings from sPOD, it seems that creating a plug-and-play, bluetooth, tablet interface to work with their relay board could make things more simple for you. With the sPOD, you would be able to turn on/off up to 6 items, and you would have the option of integrating their switch board as a failsafe. The relay boards can be purchased separate from the switch box, operate without molesting the factory harness, and already have most of the mounting figured out for several vehicles. This also means that people who already own an sPOD may be interested in adding your product to their current setup -basically adding to your potential customer base. You would still have to come up with the interface between the tablet and sPOD relay board, but it appears that you were going to something similar anyway. I'm not sure how big you want to go, but you could always post your project idea up on
kickstarter.com.
I said a lot, but it's only food for thought.
Cheers