Heres a way to automate this with... automator.
First run Automator. Then add "Run shell script" action.
Change "Pass input" to "As Arguments"
Enter the following into the box where it has the default "cat" command:
Code:
/opt/PalmSDK/0.1/bin/palm-install -d usb "$*"
Thats basically it for a Finder plugin. Go to the File menu, Save as Plugin, Write up a description. I used "Install to Palm Pre"
Then just control-click or right mouse click your .ipk files and select the automator plugin to install them. It should also work if you select more than one file.