Bicycle indicators - useful or not?

A while ago we came across this innovative product for an integrated bike light, mirror and indicator.  It's an interesting idea to remove the need for the cyclist to remove their hands from the handle bars

The interesting question seemed to be one of conditioning for the car drivers.  Drivers are used to looking for hand signals (even if they aren't very good at seeing them) so would they really notice more of a motorbike-style indicator on a bicycle and would they recognise it as an indicator?