From ModMyiFone - Wiki
This guide will teach you how to access your iPhone file system straight from Finder in OS X, using AFP. Kudos to Core for putting this hack together, and to the guys at FrenchiPhone.com for putting it on their Installer source.
This hack has only 2 steps.
Step 1. Install AFP Service.
Make sure you have Installer.app installed on your iPhone (check the many guides on the site), and you have the FrenchiPhone.com source added. To find out how to add a source, use this guide. The FrenchiPhone source is http://rep.frenchiphone.com. THIS IS NOT A URL YOU GO TO IN SAFARI, IT IS AN INSTALLER SOURCE. I just linked you to a guide on how to add a source, check that guide for more info if you're unsure.
Note: For installation (and instructions) in English you can also install AFP from Shai's Apps (http://ride4.org/shai.xml)
Ok, lets move forward.
Open up Installer, and scroll down to the FrenchiPhone.com category.
Inside it, click Demon Apple FileSharing.
Now click Install in the top right.
Now you have it installed, good. That's it for Step 1.
- Digitol Edit: In some cases you may have to start up the afp daemon on your iphone using ulcti app. (for those who are not getting connected)
Step 2. Get access in Finder.
Open Finder.
Hit Apple+K on your keyboard to open the Connect to Server window, or access it from the Go > Connect to Server menu. When the window pops up asking for the server info, put in afp://your.iPhone.ip. Mine is 192.168.1.2, so you can see I put in afp://192.168.1.2. Then hit Connect.
I like to click the plus sign to the right of the address bar to save this as a favorite so I don't have to type the info in every time.
The Connecting to Server window should open up, and then ask for your user name and password.
If it doesn't ask for your user name and password fairly quick (a few seconds), then make sure you are connected to the WiFi network on your iPhone, and that you are in fact using the IP address you put in Finder.
When it asks for your user name and password, put it in and hit Connect. The default user name is root, and the password is alpine for 1.1.1. and 1.1.2 firmware, and dottie for older firmware versions.
Finder will ask you which volumes you want to mount. Choose iPhone Root FileSystem and hit OK.
That's it! You now can access the iPhone straight from Finder! Most of your personal files will be in private/var/root/Library or private/var/root/Media. And of course installing applications is as easy as dragging the .app into your /Applications folder!
If you want to easily reconnect to your iPhone, right click on the iPhone Root FileSystem icon on your desktop. Choose "Make Alias" and save the alias to your desktop.