start w/ a good web-based mobile interface, then maybe explore making custom apps (not worth initial effort, in all likelihood).

Look at  http://www.phonegap.com/

 http://shipordie.com/post/4662729644/mobile-social-local-pivot-well-one-of-those

Django-specific stuff:

•  http://code.google.com/p/django-bloom/ - kinda mobile-specific
•  http://pypi.python.org/pypi/django-mobile - actively developed, has idea of override
•  http://stackoverflow.com/questions/164427/change-django-templates-based-on-user-agent - some somewhat old ideas
•  http://code.google.com/p/minidetector/ - detector

(For the other Django project I've been immersed in lately, an assumption/requirement is that we use the same URLs for mobile and "normal" views, instead of doing the  http://m.example.com/ thing. I like this requirement.)