OK, so this is what I've got so far:

For my current input, I can basically use a resistor (as mentioned above) in the following setup:

From my calculations (V=IR) I get that at 27.7mA my output would be 5v. So theoretically I can just measure my output with the arduino analog input and then do some calculations to get the mA.

The voltage divider is easy enough :

Which means that I should get 5V out with a 9V input. To calculate Vin I use the following formula:

Vin = Vout/(R2/(R1+R2))

Am I correct with these assumptions or do you guys disagree with something. btw - I know the theory (supposedly

), but I'm still learning to apply this practically.