Flowr

Flowr is a server application that helps you import photos from your Mac to Flowr for iOS. The tool lets you import every photo you’ve ever taken into your iPhone from your Mac or external drive using very little memory.

If you use a DSLR camera, you just transfer your new photos from your camera to your Mac or external hard drive as usual. Then, start Flowr on your iPhone and it will automatically import only your new photos to keep your photo library up-to-date.