Mobile First encapsulates a lot. Some of it technical, but most of it, at least I like to think of it that way, is a methodology.
So from that perspective it’s all about how you approach the problem. When I built rightergroup.com, I decided to completely eliminate sliders from mobile view, since they don’t add anything important. Only when I have enough real estate, I load the sliders… using matchMedia.
It all really depends on what exactly you’re after.
Picturefill is another great poly-fill that serves its purpose.
Hope that helps.