Deterrent-device accessory electromagnetic-radiation-based activation

A kit includes a deterrent device, a grip activation system, and a housing supporting the grip activation system. The housing positions the grip activation system so that a sensing space of the grip activation system extends at least partly adjacent to a trigger guard of the deterrent device. The grip activation system includes an emitter configured to emit first electromagnetic radiation having a first wavelength; a detector configured to detect second electromagnetic radiation having the first wavelength; and a controller. The controller determines, based at least in part on the second electromagnetic radiation, that an object is present in the sensing space; and provides an activation signal to an activatable system in response to determining that the object is present in the sensing space. The activatable system can include a light source. Some examples include a housing, a grip activation system, and an activatable system.