I had them on an old steel racer back in the eighties, and if adjusted properly they worked OK. Any cable stretch, however, and they were the proverbial chocolate teapots!
Jim, Specialized fit bar-top inline brake levers to several of their entry-level race and sportive bikes (they look similar to Feline's son's levers, but operate differently). They simply need the cable outer to be split so that they can be fitted - your STI levers remain in place and fully functional. They are probably available from the larger online bike shops. They work well.