Beaming is a function of Z-Wave to queue messages that are sleeping. The z-wave term used is to "mailbox" the messages until they can be received by the end point device. This is most common with locks and thermostat's that are battery powered. These devices are knows as FLIRS or frequently listening. Locks and battery thermostat's sleep and wakeup every couple of seconds to check for messages. The need for "beaming" repeaters is due to this periodic wakeup-checkin thing dones by FLIRS devices.
It is possible for the devices to communicate directly with the hub. However the z-wave controller provides no guarantee that all of these types of messages will be processed or in a timely fashion which is why beaming repeaters are so useful with locks and devices.
Not all repeaters support "beaming". This is why switches do nothing for these types of devices. Most in wall outlets does support beaming as well as dedicated "repeaters" like the aeotec devices. Some plugin units support beaming but not all. You have to check the device specifications for what they actually support. The Z-Wave product DB is the best source for this information.
