A system and method of monitoring sobriety using a hand-held breath testing device that, on receipt of a user’s breath, generates a breath test signal comprising substance content data and user identification data, and wirelessly transmits the breath test signal to a breath test signal receiving station. According to one embodiment, a method of tracking and interacting with one or more processes can comprise detecting one or more activities, each activity related to at least one of a plurality of ongoing transactions of the one or more processes. The power supply device is carried by a conventional power supply cord. The erroneous bits are detected through a bit-by-bit comparison of the erroneous data frames 302 and the corresponding corrected data frames 303, which are added together and then averaged over the total number of bits nb_total_bits received by the receiver so as to obtain a minimum error rate for the transmission.