iPhone++ (the hallmarks of the new device revolution)

The success of the iPhone shows how including API access for a consumer device will give it a long reach. An predecessor that also leveraged this approach was the original Palm Pilot (which enabled a basic five-function device to become much more).

Including compact database capability is also a compelling feature, since it allows storage of data sets and relational capabilities.

Network access is a "must have", too.

Bonus points: A virtual version of the device (allowing developers and testers to be productive without requiring actual hardware).

Conclusion: Look for devices that include network access, accessible APIs, compact database capability, and virtual simulation to go a long way.