An apparatus configured to be connectable to a first electronic device that does not include a battery and a second electronic device, wherein the apparatus comprises: a memory; a rechargeable battery; a real time clock; and engagement means configured to: releasably hold the apparatus in engagement with the first electronic device to establish a first physical communication link, between the apparatus and the first electronic device; and releasably hold the apparatus in engagement with the second electronic device to establish a second physical communication link, between the apparatus and the second electronic device; wherein the engagement means is configured such that only one of the electronic devices (12; 14) can be releasably held with said engagement means at a time; wherein the apparatus is configured to: when held in engagement by said engagement means with the second electronic device, receive time data from the second electronic device via the second physical communication link for storage in the real time clock, and recharge the rechargeable battery by the second electronic device; and when subsequently held in engagement by said engagement means with the first electronic device, transmit time data from said real time clock to the first electronic device via the first physical communication link, receive data collected by the first electronic device via the first physical communication link for storage in the memory, and power the first electronic device with the rechargeable battery. a memory; a rechargeable battery; a real time clock; and engagement means configured to: releasably hold the apparatus in engagement with the first electronic device to establish a first physical communication link, between the apparatus and the first electronic device; and releasably hold the apparatus in engagement with the second electronic device to establish a second physical communication link, between the apparatus and the second electronic device; releasably hold the apparatus in engagement with the first electronic device to establish a first physical communication link, between the apparatus and the first electronic device; and releasably hold the apparatus in engagement with the second electronic device to establish a second physical communication link, between the apparatus and the second electronic device; wherein the engagement means is configured such that only one of the electronic devices (12; 14) can be releasably held with said engagement means at a time; wherein the apparatus is configured to: when held in engagement by said engagement means with the second electronic device, receive time data from the second electronic device via the second physical communication link for storage in the real time clock, and recharge the rechargeable battery by the second electronic device; and when subsequently held in engagement by said engagement means with the first electronic device, transmit time data from said real time clock to the first electronic device via the first physical communication link, receive data collected by the first electronic device via the first physical communication link for storage in the memory, and power the first electronic device with the rechargeable battery. when held in engagement by said engagement means with the second electronic device, receive time data from the second electronic device via the second physical communication link for storage in the real time clock, and recharge the rechargeable battery by the second electronic device; and when subsequently held in engagement by said engagement means with the first electronic device, transmit time data from said real time clock to the first electronic device via the first physical communication link, receive data collected by the first electronic device via the first physical communication link for storage in the memory, and power the first electronic device with the rechargeable battery.