Whenever I speak with Service Providers or customers about SaaS applications invariably the conversation touches on mobility. Mobile email (GOOD, BES, Active Sync) is a well established and well delivered SaaS mobile solution. But core applications delivered online don't perform as well. Historically, SaaS software developers have coded like heck to solve the problem at the code/server level by creating WAP and MOB delivery options for their applications. Slimmed down functionality, limited display options, etc. As an example, WSS v3 allows certain list types to sync to a mobile device. But all of these are approximations of the web experience, and if my full application is on the web, I can be frustrated with the browser on my phone.
Enter ideas on how to solve the problem from different angles. First, on the phone. Here's an example from Microsoft:
http://labs.live.com/deepfish/
Effectively enhances browsing capability to allow me to zoom in and out and around. Like you saw Steve Jobs present on the iPhone.
And then the concept of 'bridge sites' that serve content in mobile friendly ways.
http://t9space.com/indexfull.php
t9space is primarily for social media sites right now, but the concept is applicable to SaaS providers. Will be interesting to see who emerges as an industry leader in the bridge site space for SaaS offerings. Others out there people are watching?