The mobile app developed by Nik Software (a Google Company). Is currently available for iPhone and iPad, as well as Android devices and even on the web via Google+Photos.
The latest update to iOS and Android includes a new feature called HDR Sacpe, which really does a fabulous job of increasing the dynamic rnage throughout your photo. With a little more tweaking (I'd increase the contrast and maybe do some selective adjustments to bring out the green tones in the grass some more, then lessen the saturation on the oranges in the sunset), this would be a postcard quality shot, all taken and processed on my phone in less than 2 minutes.
It also looks like the latest update has done away with the resolution limitation. Previously, photos were reduced in size if they were larger to begin with. That limited your ability to print with higher resolution images. In the photo above, the image started at 3264 x 2448 and the final product stayed the same — exactly 7.99 megapixels.
Another enhancement in the latest update is a new shadows slider, which you’ll find in the ‘Tune Image’ section. I played around with it a little and the results are great. In photos where you have a lot of detail lost in dark shadows, Snapseed will brighten just those areas to help restore what you otherwise may have missed. Like other effects, it works better with some images and less with others.
Just for fun, here’s another sample before and after image created completely with Snapseed, the HDR Scape effect and the new Shadows slider, taken with my Xperia Z1. Like the previous photo, Snapseed didn’t reduce the resolution of my image. It started at 3140 x 2160 and the final image remained the same.
The updated iOS Snapseed has improved towards postcard quality. Seeing the difference between the before and after images and none of the resolution faultered at any point. If you still haven't tried out Snapseed, I suggest you try it out (since it's free).