Mobile BI has been widely agreed as a second killer app for enterprises other than mobile email. Gartner has made analysis on this area and here is a quick summary from my side.

For end users,
1. small screen support is critical.
2. collaboration and exploration can be more intruitive to users.
3. offline reporting support
4. Multiple device support
5. Dashboarding

For Developers,
1. build once, deply many
2. transform desktop reports to mobile devices with less efforts.
3. Security
4. application development, integration with external, layout customization and development APIs are essentials

From my experiences, Mobile BI can be a evil devil for enterprises. It is fresh new at the first glance, but also can be of little interest to users several days later. Collaboration functions and email integration functions largly promote users sharing what they find in the reports. Also exploration functions can enable users discover datas and business insights with less limitation. Otherwise Mobile BI is only for a small group of executive users, rather than a killer apps that can be deployed more widely throughout different departments and organizatons.