Hey Eric,
In terms of pureplay, the only one I'm really familiar with is FLT and yeah, they have a head start on many companies and have yet to really generate any meaningful revenue. This is why they've lagged. I actually owned FLT but then exited last year after they missed their quarterly fillings.
They seem to be just there - on the verge, but can't quite get over the hump from experimental to full blow commercial contracts. Once they do, that is when the company will move but personally, I'm gonna wait until i see some meaningful progress in this are before I'd consider adding them again.
Mat