A wireless device comprising: a communication unit configured to communicate with a host apparatus ; a controller configured to control the communication unit; a storage unit configured to record data obtained from an external device; a battery that is a power source; and a battery remaining amount calculation unit configured to calculate a battery remaining amount of the battery based on a communication status with the host apparatus , characterized in that the battery remaining amount calculation unit is configured to obtain an estimated battery life by estimating a transition of the battery remaining amount based on the battery remaining amount calculated after an elapse of a predetermined period from the installation time and current consumption up to the time of calculation of the battery remaining amount, comparing the estimated transition of the battery remaining amount with a predetermined battery life determination remaining amount, and calculating remaining usable years, and adding the remaining usable years to the predetermined period, the controller is configured to determine whether the estimated battery life calculated by the battery remaining amount calculation unit is shorter or sufficiently longer than an expected battery life of the wireless device , and the controller is configured to change at least one of (i) a frequency of transmission of the data to the host apparatus via the communication unit and (ii) a volume of the data transmitted to the host apparatus via the communication unit in accordance with the battery remaining amount calculated by the battery remaining amount calculation unit . a communication unit configured to communicate with a host apparatus ; a controller configured to control the communication unit; a storage unit configured to record data obtained from an external device; a battery that is a power source; and a battery remaining amount calculation unit configured to calculate a battery remaining amount of the battery based on a communication status with the host apparatus , characterized in that the battery remaining amount calculation unit is configured to obtain an estimated battery life by estimating a transition of the battery remaining amount based on the battery remaining amount calculated after an elapse of a predetermined period from the installation time and current consumption up to the time of calculation of the battery remaining amount, comparing the estimated transition of the battery remaining amount with a predetermined battery life determination remaining amount, and calculating remaining usable years, and adding the remaining usable years to the predetermined period, estimating a transition of the battery remaining amount based on the battery remaining amount calculated after an elapse of a predetermined period from the installation time and current consumption up to the time of calculation of the battery remaining amount, comparing the estimated transition of the battery remaining amount with a predetermined battery life determination remaining amount, and calculating remaining usable years, and adding the remaining usable years to the predetermined period, the controller is configured to determine whether the estimated battery life calculated by the battery remaining amount calculation unit is shorter or sufficiently longer than an expected battery life of the wireless device , and the controller is configured to change at least one of (i) a frequency of transmission of the data to the host apparatus via the communication unit and (ii) a volume of the data transmitted to the host apparatus via the communication unit in accordance with the battery remaining amount calculated by the battery remaining amount calculation unit . <EOS>