I think an early step should be for you to simply decide what it is you want out of the conversation. Do you just want private / personal acknowledgement that t

I think an early step should be for you to simply decide what it is you want out of the conversation. Do you just want private / personal acknowledgement that they used your idea (in part or in whole)? Do you want some sort of public acknowledgement / attribution of your contribution? Do you want a cut of whatever profit (if any) they make? Do you want a share of their company? Etc., etc. Once you know that, how about just ring them up, ask to meet and say roughly "Hey guys, from what I'm hearing, your current startup is doing something awfully similar to an idea I shared with you on $DATE. Given that, I was thinking it might be fair if I got (insert sentiment from above). What do you think?" A lot of how this will be received probably depends on many, many variables - including details of your relationship with these folks, your respective attitudes and beliefs about the nature and value of "intellectual property", whatever advice/input they get from the incubator, any other investors they are dealing with, lawyers, etc. In either case, good luck.