Abstract: A status alerting unit for a seat belt having a connectable buckle and tongue, particularly for use in the supervision of children riding in a vehicle. The unit has a housing mountable to the seat belt buckle. A proximity sensor, such as a pivoting flipper element, is deflected when the seat belt tongue is inserted into the buckle, and generates BUCKLED and UNBUCKLED signals. An audible alert device generates appropriate alert signals in response. A low battery voltage warning is also provided. The unit is self-contained and functions properly with a wide variety of existing seat belt assemblies, without interfering in any way with a user's accustomed seat belt operation, or requiring special care or attention while the tongue is inserted and latched into the buckle.