It is important to remember that 'improved' often is intended to mean higher gain which itself means more directionality.
Directionality (high gain) is a bad thing for certain, typically mobile, applications (GPS for example) where the signal might be coming from almost anywhere. If the orientation can be controlled, then +3dBi gain can be achieved for hemispherical coverage (assuming that there is no signal emerging from underground - a safe asumption for most applications...).
Active steering can provide both high gain and automatic tracking - at a cost.
1) Yagis for cell phone - these are still available and are useful for remote cottages and off-shore islands, etc. I've read about people using them to deselect their local over-priced British Virgin Islands cell phone provider and use the cheaper American Virgin Islands provider several miles across the sea.
2) It only takes a couple of dB to make a huge difference in pixelization breakup for any digital TV signal. Same thing applies to satellite TV dishes where an extra couple of inches diameter can provide much much better reliability during heavy rain storms.
3) GPS is mostly about signal processing tricks. The antennas must be low gain, although perhaps an array of antennas could be used. The present approach is to use fancy DSP tricks to make a better GPS mousetrap.
4) There is the 4-element Luneburg Lens array to provide mobile DBS with about 4" height. This is how they bring DBS TV to large aircraft or RVs. For RVs, the signal still drops out under overpasses and behind buildings - so the travelling rock stars reported spend more time playing video games than watching TV.
The 'Next Big Thing' will be mobile Wi-Max (56Mbps, 35km range) which brings high speed Internet to your car. Imagine what happens to your local AM/FM radio station when you can listen to anything you want from the Internet on your car stereo or your Wi-Max enabled walkman.
Cheers.
