Two sliders will do the job...

I like a new slider with min and max as inputs...

Would it be okay if it outputted a point instead of 2 separate values?

In fact, if we approach this like the Colour picker, it can even be a three-dimensional slider.

While I agree that 2D and 3D sliders in GH are a great idea...there are ways to do a 2D slider, even all sorts of custom interfaces through other hoops if needed (as we've already seen with the colour picker method):
http://www.livearchitecture.net/archives/4489