Hi there, Libbie!
Photosynth's mobile app makes panoramas instead of photosynths.
On Windows, you can use Microsoft ICE to stitch full resolution panoramas and upload them to your Photosynth.net account.
Whenever you are shooting panoramas (no matter what software you're using to stitch it), your goal is going to be to keep the camera's lens as close as possible to the same position (height, latitude, longitude) while pointing in as many directions as possible to capture as much of the surrounding scenery as possible.
This means that you don't want to hold your phone at arm's length and orbit it around your body because that will make foreground objects line up differently with background objects in different shots and you won't get a smooth stitch.
Here's a few links to help illustrate what I'm saying:
http://styleisviolence.com/photosynth-app/ (read the 'bloopers' section)
http://www.johnhpanos.com/epcalib.htm (Good explanation.)