DeTune lets you somewhat browse the iOS file system. With this application, you can browse any iOS device that you connect to your Mac via the USB cable. iPhones, iPods and iPads are all supported. There are many reasons why you would want to access the file system. In my case, I was looking for an app like this to download the photos from my iPhone. Without this application, the only way to download them would have been to e-mail them in batches of 15 or 20. That could have taken a long time, and it would have entailed a lot of work. With DeTune, after some tweaking, I simply browsed to the DCIM folder and copied all the photos to my Desktop. It took me less than 2 minutes.
The application, by default, only shows the music files that you have on your iPhone. If you wander into the Preferences, you can check a few settings that let you see the files list. Not all the files will be shown. The delicate system folders will be hidden, and that somewhat limits the use of the application. But that is not a problem if you are going to use it to download music or photos.