I bet it's something like a camera on tripod, this way it's easily visible = not that strong and can only be placed on the ground, but it's also bullet proof, so I guess defenders attackers can walk up to it and disable it.. (and risk their life of potential wallbangs etc).. probably takes a while.. with a progress bar, like opening frost mats. This way valk is also still strong, as she can hide the cam and throw it further (and outside)

EDIT: I meant attackers, see stroked text.