I like being able to see the date/time of dive, dive profile (visual chart of depth vs. time), comments, and other relevant info (gas used, dive type, etc.) on my iPhone divelog. I don't know of any software-hardware solutions that allow
direct download from a dive computer to an iPhone.
Here's the system I use:
1. Download the profile from my dive computer to my Mac using
MacDive software.
2. Fill in all of the data/comment fields in MacDive.
3. Use
Dive Log Manager to convert the MacDive database into a format usable by the
Dive Log iPhone app.
4. Upload the converted database file to my iPhone.
FWIW, I only do Steps #3 and #4 once every few months.
Essentially, this is a one-way flow of divelogging info from the Mac to the iPhone. I don't modify the info once it's on the iPhone -- it's read-only.
The system does work for me, though. Whenever I have my iPhone, I have access to info from the vast majority of my dives (except for the latest ones).
Hope this helps...