Current measuring with PIC
There are many current-to-voltage converters out there. The simplest is a resistor. Make it small to reduce losses or big to make the voltage big enough to cover your entire ADC range. Or, make it small to reduce losses and amplify it with an op-amp circuit to cover your entire ADC range.

Another often overlooked current-to-voltage converter is a MOSFET that's on, which is pretty close to a resistor. Perhaps not as accurate, but many circuits that require current measurement already have a switching MOSFET in them, so this method is cheap and convenient. The datasheet will list the on resistance as \$R_{DS\_ON}\$.

For a step up in sophistication, look for hall effect sensors. Hall effect sensors measure magnetic fields; some of them are configured to measure the magnetic flux associated with a current passing through a wire. Here's an example product page to give you an idea. However, at \$200mA\$, I don't see much need. Typically this sort of product comes into play when the current is high enough that a resistor, even a small one, would represent a significant loss.