The challenge is to develop a general purpose communication tool which is portable, relatively secure, easy to build, easy to use and avoids the mistakes that we've found out about with smart phones and computers.
The biggest challenge will be in packaging components that are readily available into a small, durable, usable device. Doing this in a reasonably cheap unit is also important.
So, the project entails two major subsystems: 1) a portable communication terminal which can accept 2) various code modules.
The standardization of the interface between the terminal and the code module is crucial to allowing other hackers to develop their own code modules for the terminal system.
It is seen that a 3D printed packaging will be necessary to make the unit durable and portable.