In reply to Ihem:
Since fingerboarding isn't fundamentally different from other forms of strength training (yes, it's training isometric holds, but there's plenty of research on that too), it would be a very unusual finding if it didn't lead to improvements in finger strength.
But obviously climbing's multi-factorial, which makes it tricky to evaluate transfer to climbing -- all other things being equal, stronger fingers will probably help, but (for example) maybe someone already has fingers which are more than strong enough for the grades they climb at but their technique is terrible.
So it's going to be impossible to get a neat bit of research that says "if your fingers get X percent stronger, you will automatically climb Y grades harder". Though the Lattice database might produce some useful correlations if anything does ...
As to whether fingerboarding will be helpful *for you*, that's a different question. The answer will depend on things like: how long have you been climbing for? What sort of grades are you climbing at? How often are you climbing each week? Is lack of finger strength actually what's holding you back right now? (For example, maybe you don't have problems hanging onto small holds, but you can't move off them.) Are you using your climbing time to work on your weaknesses? Would fingerboarding crowd out other training stuff that might be more useful for you? Can you motivate yourself easily to do training activities, or do you find them soul-destroyingly boring?
If you can give a bit more info about where you're at, you can probably get some excellent advice from people about whether fingerboarding is likely to be helpful for you, and what protocols you might try.
There's not going to be a research paper out there at the moment which can give you a yes/no answer on this, but there's a lot of practical wisdom to call on.