Today was an interesting day. I started looking at the accessories I need to make this work. It looks like I will have to spend some money. The bluetooth shield will be about $60-70. I looked at the BlueSmirf and the bluetooth mate, both are more than the main board. That is what it costs to do stuff I guess.
It seems weird, because almost all phones have bluetooth capabilities, even the cheap ones, and they usually don't cost like that. I know Arduino shields are low production items, but wow! I was thinking maybe $20-30, I guess I can't guess well.
I've been looking at amplifiers for the project. I originally was considering the LTC1050, since that is what I was using before. Then thinking of multiplexing it, with some 4066's or something. Today I found the LT1014's, 4 in a package, and the datasheet shows cold compensating, so you can get 3 per package, and the are about $5 each, in a DIP package from Mouser. To do 8 inputs, it will take 3 packages, not bad.
There is also an Arduino proto shield, I found. That ought to be useful, allowing me to build the adapter on a good looking board, instead of by hand on a perf board.
I looked at the MAX6675 A/D converter. It would work, but they are really expensive, 8 would be about $100! I keep looking, and think the LT1014's are the right choice.
For schematics and such, I've used eaglecad in the past, and will probably use it for this. The free version limits your board size and number of components, but I think this will fit in the limits enough.
Another shield I found a few months ago is the autopilot. That will probably be my follow on project. If this doesn't turn into a FADEC at least. I want to head into the FADEC direction, but will be very careful, and have overrides until I am sure it works (and even then if I design for override, I'll probably keep the design).