Looks okay so far. You mentioned a 3rd servo and you'll need an analog input for each of your Hall effect, piezo and light dependent resistor inputs. The answer to your original question now relies on the number of LEDs you want.
Cheers Geoff, did some research and thinking, I'm going to try and use the least hardware as possible. So I'm thinking 2 servos will be enough, with the Hall effect, piezo and light dependent resistor inputs and 2 LEDs. But I'm thinking I may only use 1 LED as I'll just put a LED into the LED2 pin and hook a wire up from that to a unused pin.
So I'll need 6 analog input pins for all the servos, sensors and LED and with the wave shield having 6 free, I think I'm there!
PaulS:
If I do it like this diagram am I right in thinking it will work?
Until the wimpy-assed 9V battery goes dead. Which won't take long. Price per amp hour, they are at the bottom of the list. AA batteries are a far better choice.
Cheers Paul, What would you suggest instead of the 9V battery? I want to run it for at least 2/3 hours.