For those independent filmmakers building their kits and making decisions about what is a must-have, what would be nice but isn't quite necessary, and what is simply just a gimmick, one item that has probably crossed their paths is a tripod-based slider.
These items are essentially a substitute for a dolly and have a track length of two to five feet along which a sled (with the camera mounted) can smoothly travel.
Examples of such items are the INDISLIDER and the T-SLIDE.
These items will generally run somewhere from $500 to $1,000, depending on track length and other accessorization like optional tripod heads.
A FORUM POST that deals with these items also has some discussion on the practical advantages and drawbacks of these accesories. Generally speaking, in order for them to be fully functional with a camera move that sends the camera to the far end of the track, the ends of the track should be supported with additional (not provided) structures like monopods in order to ensure stability. Others are sandbagging the primary tripod on which the sled is mounted for peace of mind.
All in all, it seems like a good tool for very short dolly moves, short "pushes in" and reveals from behind doorframes, etc. But it does not seem like it is necessarily an ultra-convenient tool that you just keep on your tripod, barely notice it's there, and turn every locked down shot into a dollly shot with barely any setup time. By that standard, it would fall into the category of "if it seems too good to be true..."
But there are many satisfied customers and people do speak well of the entrepreneurs themselves that have developed these products, in terms of professionalism and support.
Here is an example of a MOVIE TRAILER (No Greater Love), where the makers stated that the majority of the visible dolly moves were performed on an IndiSlider.
Also, at first glance, this does seem to be one of the accessories that would lend itself more easily to a DIY solution than some devices with more complex engineering.
In that vein, here are a couple of forum discussions on developing your own "DIY IndiSlider"...