Are revolights a good idea?
I don't believe these are "better" or "worse" than other lights, rather they are a supplement to other lighting systems. I think the inventors' claims about forward and rear illumination are somewhat questionable as it won't compare to a real head/taillight of similar cost.

However, I think they would provide some improvements in side and off-angle visibility. They are "eye catching" because they are distinct which is a very important factor to being noticed by other road users. There are actual lights which also provides superior visibility to any reflector-based solution available on the market today. Based on what they claim (and what is visible in the videos), these will provide nearly 360 degree visibility.

Mathew's answer makes some excellent points about weight and relative brightness. However, I disagree with his point about using a reflective materials as a potentially better solution. I have used many types of reflective materials ranging from reflectors to polished metals to 3M SOLAS-grade reflective tape. When you are within the "optimal" range of angles, they provide an incredibly bright surface for a long distance. However, when viewed from an off-angle or when the light is not directly shining on the reflective surface, their illumination characteristics are relatively poor--even when using a the high beams on a car.

There are many situations where a car's headlights are not illuminating the area the driver is looking (i.e. the driver is looking left or right) and the amount of light striking the reflective surface is minimal. Products like the revolights and the down-low glow tube are attempting to solve that type of problem--i.e. anywhere that reflective materials may not be reliable and your "normal" headlights won't provide adequate visibility.