I've recently started using the Piwigo app (for Android). It's getting good! Version 1.0.0 has just been released, and it has the thing that I've been wanting for ages: the ability to select multiple photos at once, to upload. Hoorah or what?
So I've got to get serious about organising my photo collection now, and make sure a) everything is in my Piwigo; and b) each photo is there only once. I might see if I can help with preventing duplicates at upload time.