Hi John -
When you download the data, you use a dongle that OmniPod will send you - Insulet will send it when you ask to use the old software. All you do is plug that into your computer and then beam it from the PDM to the dongle.
It would be great if you created software that would allow you to download the data from a Mac. Sounds like a lot of work though. I would think that Insulet would make this new app available for handhelds since that would probably be the most convenient for most people. That said, you would be able to look at your stored data via the internet and that's pretty cool.
I'm sure you are going to love your OmniPod, I know we do!! Good luck with it! I wrote some tips & tricks we've learned while using it these last 9 months - check out my post under the OmniPod section.