The second part of the system is a variometer (Eos, Helios, and Era). Its job is to gather the information which the Zeus uses. The vario has pressure connections as well as the GPS antenna connection which is required for IGC logs.
There is a wide variety of choice for varios and for LX Zeus display sizes.
All their varios are standalone devices which can be used without a glider computer for displaying basic flight parameters such as final glide information, Speed Command (SC) as well as simple navigation. Their varios also have an internal battery which means that your IGC logs do not depend on your glider's batteries.