We have used mobile learning as just in time learning for our sales team i.e. prior to the ILT on a new product. The learning level was basic i.e. Knowledge in the Bloom's taxonomy. The important design criteria we considered while creating mlearning modules were:
1. Decide the family of devices you will use it for - the platform and technologies for various devices (even within the same brand) are different. So one needs to be very specific about the devices for which the solution is being designed. This turns out to be the biggest challenge for mobile learning solutions.
2. Identify the precise learning objective. What do you want to achieve from the solution? No really, what? considering both elearning and ILT would be more detailed and thorough for the learners.
3. Ensure the images and content elements are light. Obviously! Imagine having to wait for 15 seconds for an interaction download on a small screen!
4. Plan on short learning modules. Maybe 10-12 screens at the most. It is my assumption that the attention span gets shorter as the devises get smaller.
5. End it with a short 1-3 questions which can be reported to the LMS. You want to integrate learning from different media as much as possible.
I believe blended learning solutions work best since each media brings its own unique attributes. The important thing is to repeat key learning points and move up the Bloom's taxonomy.
It is a complex and potentially expensive challenge to integrate mobile learning for all learners because of the large variance in mobile device technologies. One of the solution to consider in such a scenario is to allow mobile users to access information from a web location (rather than download it on their devices). That might work and could be a relatively less expensive.
Added on May 24, 2009: Click here for a rich discussion on this topic at Linkedin. You will need to log into your Linkedin account.