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 . <EOS>