Do you want to customize the Host application or the communication protocol itself (modify I2C protocol itself)? Anyway, take a look at this App Note which explains how to customize the comm protocol for the bootloading - http://www.cypress.com/?rID=50230
If you are looking for customized Host tool, the source files are available at the creator root directory.
eg: C:\Program Files\Cypress\PSoC Creator\2.1\PSoC Creator\cybootloaderutils
Currently trying to use an arduino to bootload 8 different PSOCs over I2C.
Can anyone point me in the right direction?
Tried 'reverse engineering' the code given here http://www.cypress.com/file/137036/download under creating a bootloader host but arduino is throwing more errors than I can shake a stick at.