Question: How do you bring the handles/grips back to the top?

Sounds like you're suggesting a "zip-line" for going down a set of stairs?... While I think the idea (in theory) would be kind of fun, I'm not sure how practical it is. Most staircases are rather short (with some building design exceptions of course), so it wouldn't be much of a ride if it ended just as fast as it started.

If you're still into this idea, look at the design of a basic zip-line, as I would think a cable system would be easier and less expensive than ripping a ceiling apart in order to fashion some other method.

And if you do make such a thing, you must publish an Instructable. :-)

I also found this http://dangerouslyfun.com/zip-line which will show you the basics of an (outdoor) zip-line. notice the comments regarding the dangers.

One way wuld be to fasten a rail to the ceiling and (a C-shaped with the open end downwards - like used in garagedoors and ports) you can then use a (rubber)wheel of sorts and given a little friction (i am not sure a free run is all that fun - might depend on how far a ride you make) it might work

(totally pulled out the opposite side of my front, though i have in my younger days worked in a place that produced the mentioned C-shaped rails and packaged it with wheels/brackets for garagedoors, ports)

But as mentioned, SAFETY, this has the potential to cause a lot of damage to the user or the one getting hit at the bottom (im such a party-pooper)