A great addition to the DC motor shield would be a tiny duino or lily shield that encodes absolute angular position using the hall-effect based AS5048B. It determines the angle to 14 bits of resolution or approximately .022 degrees. The chip is $13 single unit quantity, but the eval board is $220. Seems like an opprtunity. Stack one of those on a tinyduino board a with a motor control shield and you'd have a great stack.
