Found at http://hexperimental.com/content/coding-iphone-apps-textmate
I haven't tested this myself, but this guy suggests setting TextMate as your editor of choice in xcode and then changing the run shortcut to use applescript to send keyboard shortcuts
Open the Bundle editor ( Bundles > Bundle Editor > Show Bundle editor ), the xcode bundle is all the way down, select the Run command and change the Command to this:
osascript -e 'tell application "Xcode"
activate
end tell
tell application "System Events"
key code 15 using {command down, shift down}
key code 15 using {command down}
end tell'
#I'm leaving the old command commented below just in case.
#PROJECT=$(ruby -- "${TM_BUNDLE_SUPPORT}/bin/find_xcode_project.rb")
#if [[ -f "${PROJECT}/project.pbxproj" ]]; then
# "${TM_BUNDLE_SUPPORT}/bin/run_xcode_target.rb" -project_dir="$PROJECT"
#else
# echo "Didn't find an Xcode project file."
# echo "You may want to set TM_XCODE_PROJECT."
#fi