Preparing Brown Rice
It is good to see people going towards brown rice. 
When buying brown rice you could choose out of two types based on its production method.


Par-boiled (not as same as boiled in a bag)
Raw


Former takes shorter time to cook while latter takes longer. If you are using Raw type, you need to wash and pre-soak it for an hour or so (depend on the amount). Once you soak it, the water required for cooking brown rice can be as same as white rice of same weight.

Lets take 1 kg of raw brown rice.
Assuming you have not soaked, you may add extra 2 cups of water than to what's indicated in your rice cooker for 1kg. 

Certain brown rice from Europe, Thailand or Vietnam can be pretty corase and absorbed high volume of water. Where as Brown Rice from countries like Sri Lanka tends to be tender. Country to country the grain differs in shape, taste, nutrition since soil, water, weather climate, organic, non organic and the type of seed used for agriculturing. Thus leaving us with a bit of search to be done when cooking these rice. If you are experienced you will know immediately how to meddle with each type.

As for the boiled in a bag, I don't recommend that method. Mainly because it doesn't allow sufficient room for rice to settle and expand. (I hope you are not referring to a very specific rice item condumed in certain Asian countries as it indeed meant to be cooked in the compressed bag and eaten in compressed form.)

PS: My family has been harvesting paddies with different types of rice in tropicals for generations. Personally and most people seem to prefer par-boiled rice. It is much tastier but requires more sweat compared to producing raw.

In your case, you don't even need a rice cooker. We use a pot when it comes to any rice but specifically for brown. A deep enough saucepan/pot for the amount of rice + water) can be used. However in this method you have to be careful about "managing" fire and following:


Wash and soak the rice
Add the water
Get strong fire on the lid open pot to avoid overflowing
You will see bubbling rice in sometime
When water is starting to be a little above the rice (as almost as rice surface) lower the fire to a blue minimum and close the lid
I suggest you to be around the kitchen till you get a hold of the timing :-) you could prepare other dishes...
Switch off and stir using a fork (wooden if your pot is nonstick...)


Bon appetit!