The Boundary Monitor retains the same name within SAM, however you will need to recreate the component using the new Deep Space Labs component creation path. Do note that it is recommended to simply use the game object quick creation option, which will create all basic components you need to get started with SAM, including the Boundary Monitor.
To do so, simply choose GameObject -> Create Other -> Deep Space Labs -> SAM -> Default SAM Setup, either via the top Unity menu bar or by right clicking in the Scene Hierarchy.
Alternatively, if you want to only create a new Boundary Monitor component and nothing else, that information is provided below.
You can add this component by selecting a game object and then selecting from the Top Menu Bar:
Component -> Deep Space Labs -> -> SAM -> Secondary Components -> Boundary Monitor
or by selecting a game object and using the Add Component menu via its inspector:
Component -> Deep Space Labs -> -> SAM -> Secondary Components -> Boundary Monitor
The Detection Frequency field continues to be the only field on the Boundary Monitor. You can copy over the value you were using before and that's it!
The Active Grid component now contains some options for overriding the detection frequency it uses with whatever Boundary Monitor is assigned to it. This change allows you to set a default detection frequency on the Boundary Monitor and then override that frequency when needed directly on the Active Grid component.
Previously, if you wanted different Active Grids to use different Boundary Monitors, you had to create multiple Monitors.