I assume you've done your home work on other similar projects already. Is there a reason you won't be working on improving Pimlico or GPE? Developing a full featured PIM suite is a huge undertaking. I have no experience with GPE, but I've taken a look at some of the Pimlico apps and the code looks clean and 'smart', even if current feature set is still lacking. Adding a few things (like alarms) would make it quite nice... (disclaimer: I work for Openedhand, Pimlico main developer)