How do I make a custom field choose an image?

I need a way to create a custom field that will let me pick an image from the media gallery. How do I do that?

The custom field should have a button that when clicked will take me to the media gallery and place the src destination url within a input text box.

looking for a plugin or online tutorial and I’m having little luck.

A few weeks ago I added a feature similar to Magic Fields.

Here’s the github project. The most important thing is in this file: js/custom_fields/media_image.js