Three recommendations for improvements

1) The ability to set breakpoints in TextMate
2) The ability to set watch expressions
3) The ability to either debug using TextMate (prefered) or have a link to the current line of the file in TextMate

Great job, this is a nice lightweight alternative to Eclipse especially when developing in Magento

The ability to add external breakpoints would turn this into the perfect tool. I use vim for development and so far it lacks a good debugger :( I can easily write a vim plugin that will allow adding breakpoints easily.

Watchpoint variables are bug://report/191. The rest of these ideas are beyond what I view the scope of MacGDBp. The debugger protocol is a documented standard, so if you want TextMate integration, the way to go would be to write a TM plugin that talks the protocol.