I know some of you have already figured this out. I basically would like to press the upload button and then have the IDE use the USBtinyISP instead of the serial approach to upload a sketch.
I have already figured out how to do this with avrdude from the command line but this is a bit awkward. This is what I use on the command line:
/Applications/arduino-0010/hardware/tools/avr/bin/avrdude -C/Applications/arduino-0010/hardware/tools/avr/etc/avrdude.conf -c usbtiny -p m168 -e -U flash:w:led_blink.hex
I have looked at the various Arduino configuration files and there is a lot that sort of looks like this is possible. I am just not exactly sure how.
I found this: http://www.arduino.cc/en/Hacking/Programmer
It is almost what I need with the difference that this seems to assume an stk500 programmer on a virtual serial port. USBtiny uses direct usb communication and is known by avrdude as "usbtiny".
Maybe there is something in the Arduino dev version that could help me further.
Any assistence very much appreciated,