We consider the following forms of mobile interactions: client/server interactions, whereby the request of a client triggers the execution of a unit of code in a server and returns the results to the client; remote evaluation, where a device can send code to another host, have it executed and retrieve the result; code on demand, where a host can request a unit of code from another device to be retrieved and executed; and mobile agents, where an agent is an autonomous unit of code that decides when and where to migrate. Moreover, we consider devices that can be nomadically connected to a fixed network, devices that are constantly connected to a fixed network over a wireless connection, devices that are connected to adhoc networks and any combinations of the above.