From what I know, there are going to be only four players in this year's draft.
RB Harvey Unga
RB Quentin Castille
RB Vanness Emokpae
DT Joshua Price-Brent
Word has it that Unga will likely get drafted and Price-Brent has an outside shot at being selected. Castille and Emokpae will go undrafted and will have a chance to catch on as a free agent with some team.
I think the only player the Dolphins will even consider giving up a draft pick for would be Unga. However, I would say the odds are very low that they would actually make the selection. I could see them putting in a 6th or 7th round pick claim and hoping he falls that far. Realistically he is probably going to go in round 5 but might even slip into round 4.
I think with Brown, Williams, Cobbs, Hilliard and Sheets currently battling, there just is no room to take a chance on Unga with a draft pick. If there is a shock and he goes undrafted, they would probably bang down his door with a contract offer. Don't expect the Dolphins to make any selections this year.
I will say this though, keep an eye on Price-Brent as a possible undrafted free agent signing. Would be worth a look maybe as a possible NT. 6-2, 321 pounds.