Hello again-
I had more thoughts/suggestions, so thought I'd share them. In my last post, I focused on the bare minimum of what would be useful for Halloween Haunters. It occurred to me afterwards that there is a broader need out there for what you might call a "Holiday Audio Shield." In other words, something that would work for both Halloween and Christmas decorators. There is definitely a market for a well designed, easy to use, pre-assembled audio shield that would make it easy to sync servos, LEDs, or relays that control 110v ac circuits, to an integrated stereo audio source, which means the shield definitely needs an onboard SD card. You said there might not be room for it, but you need to make room. Other similar audio shields have them. It would be essential. I'm talking a shield that could control a talking animated character, or be used to animate your yard lights to music at Christmas. A board designed specifically for the holiday DIY, like me, who doesn't want to waste time soldering and learning how to write complex code. I can't tell you how frustrating it has been trying to find easy arduino solutions for my needs. So much of what's out there requires such a high level of technical understanding, that I believe it scares off tons of potential customers. Why can't someone make an audio shield that doesn't require an engineering degree to understand how to get it to work? I believe there are lots of folks like myself out there, who understand the basics of writing sketches, but get completely lost when trying to understand the level of code knowledge required for things like audio shields. I guess my point is, the most important feature of your shield is ease of use for the semi-novice. You need to provide sketches for every possible thing it can do. EVERYTHING. Searching the internet for sketches and trying to make them work make people like me crazy. The easier you make it for consumers, the more units you will sell. And I believe whoever successfully fills the holiday audio shield niche first, will find they have a huge client base and lots and lots of money in the bank. Hope this helps.
Best of luck and happy holidays.