Kickstarter product "Lil-Mule" is small, motor-powered camera platform that has been developed to capture timelapse or real-time video for lengths much longer than most rail or slider based systems can provide. It's aim was also to give the user a simpler feature set, doing away with the complicated math and setup that other systems offer. This video gives you a glimpse of what the system is capable of, with more informative videos inside.
The slider is based on a low profile, rollerblade style wheel setup, with the ability to do incremental angled adjustments for orbital shots. It is recommended that you give it a smooth surface to roll on, and also keep in mind that some smoothing in post might be necessary. Below is their kickstarter video.
This project has already been funded, which is great to see. Competition in the slider and timelapse photography market will only bring us better products at a cheaper price over time. You can still get one at a lower cost before real production begins on them, which will be until about January 31, 2013. Here is a link to their kickstarter page.
Here is another video that shows the build setup: