A system including a computing device and a companion electronic device (200, 300, 400), wherein the computing device is a mobile phone, wherein the computing device is operable to work in conjunction with the companion electronic device (200, 300, 400), in which the computing device and the companion electronic device (200, 300, 400) each have their own electronics and/or own operating system, and each is able to construct a user environment, wherein the user environment is a complete set of software and hardware components that together provide for output to and input from a user, in which the computing device is operable to send data to the companion device (200, 300, 400), on request of the companion device (200, 300, 400), which the companion electronic device (200, 300, 400) then uses to construct its own user environment, in whole or in part, wherein the computing device and the companion electronic device (200, 300, 400) share physical, hardware and software resources of the computing device and of the companion electronic device (200, 300, 400) to reduce power consumption on either device, wherein (i) the computing device adapts, switches off or puts into sleep mode the computing device's resources when in a linked state to the companion electronic device (200, 300, 400), and when the computing device is working in conjunction with the companion electronic device (200, 300, 400), thus reducing the power consumption of the computing device; or (ii) the companion electronic device (200, 300, 400) instructs the computing device to adapt, switch off or put into sleep mode the computing device's resources when in a linked state to the companion electronic device (200, 300, 400), and when the computing device is working in conjunction with the companion electronic device (200, 300, 400), thus reducing the power consumption of the computing device; or (iii) the companion electronic device (200, 300, 400) adapts, switches off or puts into sleep / reduced activity mode the companion electronic device's (200, 300, 400) resources when in a linked state to the computing device, and when the computing device is working in conjunction with the companion electronic device (200, 300, 400), thus reducing the power consumption of the companion electronic device (200, 300, 400). (i) the computing device adapts, switches off or puts into sleep mode the computing device's resources when in a linked state to the companion electronic device (200, 300, 400), and when the computing device is working in conjunction with the companion electronic device (200, 300, 400), thus reducing the power consumption of the computing device; or (ii) the companion electronic device (200, 300, 400) instructs the computing device to adapt, switch off or put into sleep mode the computing device's resources when in a linked state to the companion electronic device (200, 300, 400), and when the computing device is working in conjunction with the companion electronic device (200, 300, 400), thus reducing the power consumption of the computing device; or (iii) the companion electronic device (200, 300, 400) adapts, switches off or puts into sleep / reduced activity mode the companion electronic device's (200, 300, 400) resources when in a linked state to the computing device, and when the computing device is working in conjunction with the companion electronic device (200, 300, 400), thus reducing the power consumption of the companion electronic device (200, 300, 400).