Beware - Engineer with PPl commentary.
I have heard suggestions of lasers or forward facing camera that could be added to enhance situational awareness for the flight crew during taxi. These each have their drawbacks. I have not yet heard a suggestion to use sonar. This technology is use on autos and trucks to aid in parking. Sonar beams can be highly directed and provide range information as will as obstruction direction. This combined with a smart processing algorithm that takes into account speed and tiller position could be used to predict an imminent collision. An aural warning could be used to alert the flight crew.
I can't think of any drawbacks to this solution, and it is not expensive to implement.