No, the pinball apps i've played with rely on an "amount of time you've held the key down" to determine how far back to pull the plunger.
It ends up working out pretty realistically because when you pull back, the enter key is pressed and effectively "held down" till you let go.
I believe Future pinball now has support for a real analog plunger input, but I don't recall seeing any support for it or anyone who's hacked together something to support it. Without special hardware, +that+ could be a real trick, but I suppose it'd be doable with enough work.
The switch trick that I describe is +really+ easy though, and the end result is pretty dang good.
My pinball plunger looks like this. That switch is actually a roller switch (ie it has a little roller on the end of the metal lever), but otherwise, it's just a standard ol arcade button switch. You can get roller switches at Happ for about 5$
