It took me a few goes to get this to work so it might be useful to give some tips on what to do, which are:
1. First get the iPad configured to talk to the AxcessPoint. Switch it on and then in the iPad settings under wifi select it. To use it with web there are also some http proxy settings - look under the iPad App help as to the server and port to use.
2. Connect the AxcessPoint to the Iridium phone and switch it on and wait for it to say registered
3. On the iPad open up iNaxX and centre the chart on the location you want GRID data for
4. Select the "Forecast" tab and then go into settings.
5. It is very important to grab as small a file as possible. Go for (say) 3 days with resolution 12 hours / 2 degrees over an area 20 x 20 deg
6. Select get data by AxcesPt then save
7. Select "Request GRIB": it will appear to dump you into the AxcessPoint App without doing anything but actually it has created an email for you.
8. When you're ready select send/receive email and it will send off the request
9. Wait a couple of minutes
10. Then do another send/receive email and you should get an email with the data as an attachment. If you select it then you should be able to open it in iNavX
Eh voila!