Hi Darren,
If the slider is set up correctly and the picker namespace matches your asset namespace, it should update in a bi-directional way.
By setting up correctly I mean the slider is associated with one/two Maya attributes that exist, and if you expect moving anim controls to update the slider, the slider should be watching its translation attributes.
Also, the slider has a value range, if the attribute value goes beyond the range the handle will appear at the edge of the range and move no further.