A smartphone case includes an integrated pager processor and pager antenna. The pager processor interfaces with the smartphone via physical connection such as USB or a wireless connection such as Bluetooth. A battery embedded in the smartphone case powers the pager processor and may be shared with the smartphone via a physical connection. The pager processor may display messages via the smartphone or independently via a speaker embedded in the smartphone case. The smartphone may communicate with a paging source via a cellular network to confirm receipt of one or both of a pager signal or a cellular network signal so that the paging source may produce maps of where various communication methods are useable.

A doorbell device includes a housing, a passive element, a battery module, and a thermal expansion element. The housing includes a mounting plate, and the mounting plate includes a through hole, an inner surface, and an outer surface. The passive element is movably disposed in the housing. The passive element includes a first side surface and a second side surface. The first side surface faces the mounting plate. The battery module is disposed on the first side surface and corresponds to the through hole. The thermal expansion element is disposed between the second side surface and the housing. The passive element allows a gap to be maintained between the battery module and the outer surface, or is driven, by the thermal expansion element, to allow at least a part of the battery module to be located in the through hole and at the same plane with the outer surface.

A doorbell device includes a housing, a passive element, a battery module, and a thermal expansion element. The housing includes a mounting plate, and the mounting plate includes a through hole, an inner surface, and an outer surface. The passive element is movably disposed in the housing. The passive element includes a first side surface and a second side surface. The first side surface faces the mounting plate. The battery module is disposed on the first side surface and corresponds to the through hole. The thermal expansion element is disposed between the second side surface and the housing. The passive element allows a gap to be maintained between the battery module and the outer surface, or is driven, by the thermal expansion element, to allow at least a part of the battery module to be located in the through hole and at the same plane with the outer surface.

A smartphone case includes an integrated pager processor and pager antenna. The pager processor interfaces with the smartphone via physical connection such as USB or a wireless connection such as Bluetooth. A battery embedded in the smartphone case powers the pager processor and may be shared with the smartphone via a physical connection. The pager processor may display messages via the smartphone or independently via a speaker embedded in the smartphone case. The smartphone may communicate with a paging source via a cellular network to confirm receipt of one or both of a pager signal or a cellular network signal so that the paging source may produce maps of where various communication methods are useable.

A wireless doorbell set includes a wearable ringer (transmitter) and a wireless doorbell receiver, which is responsive to a ring signal transmitted to the receiver from the wearable ringer. The wearable ringer is configured with a removable bracket that may be mounted to a wall such that the wearable ringer may be attached to the removable bracket on the wall, to temporarily position the ringer thereon when it is not worn by a user, and to remove and separate the wearable ringer from the wall-mounted bracket when the user wishes to wear the wearable ringer, for example, on a lanyard that may be placed over the user's head. The wireless doorbell receiver receives the ring signal from the wearable ringer and generates a sound, a light signal or both.