I don't know what happened to them but I remember seeing adds for them and actually saw one or two fitted. They looked pretty crude affairs with a butterfly valve and seemed to be directly connected to the fuel tap without a reservoir from memory so there was probably some metering linked to the throttle. I think they worked though.
I forgot where I read it, but it was an old article, describing it as a pre carburettor fuel / air mixing device for stationary petrol engines running on a more or less constant load. It is certainly not an injector. An injector is a pump and nozle device. This is not. So if an injector is called an injector because it injects, this could be called a dribbler.
Lannis hit it on the head. Wal Phillips if I remember correctly was a speedway rider/manager in UK in the 1960s. He originally developed the WP Injector for speedway bikes. Hence no real importance placed on part throttle operation, idling or gas economy but every emphasis on flat out power. HTH.