Tufo makes a small plastic tool and forgive the spam but we make one as well that does presta and schrader valves Link
edit: I should add that while Mavic valves are now supposed to all have removable cores I do often hear that some people are not getting the removable type with their new rims or wheelsets. Check at the top of the valve for two small wrench flats, if present you're good to go if not, then you don't have the latest and greatest.
A small wrench or adjustable wrench is all you need , pliers can work too. Check your local roadie shop. They probably have some of the tools laying around you could have, if you just have to have the specific tool for the job.
Roadies and tri-geeks use the removable core all the time to put valve extenders on the valves for deep walled rims.
If you do in fact have removable presta cores, the 2 ounce bottle tip will fit the valve body.
The tool I designed is just a "nice to have." I used to use a piece of 1/4" stainless brake line crushed to fit but the tool is nicer. Pliers or small wrenches are a pain to use between the spokes IMO.