I just ordered two LCS Sensor Tracks (which arrived just before Christmas) for my new layout that I'll be starting soon. I plan on having a total of three STs. I have Lionel's new Base 3 on order, so I will use that to power my LCS STs. The first two will be placed on the mainlines (1 per loop). The 3rd will be used near the loco servicing facility.
My mainline STs will be used to trigger crossing gate horn blows before trains pass through a 2-track RR Crossing. The loco servicing ST will be for programing any new Legacy locomotives, as well as triggering arrivals into, and departures from, the facility. STs also tell a Legacy Remote the current fuel levels of engines passing over a Sensor Track, which is cool. If you look at the manual for the ST, there is a list of preset commands that you can program into STs on your layout. Sean of Sean's Train Depot on Youtube has 3 great videos about ST features and recording.
If you have the LCS Wi-fi Module (the Base 3 has Wi-fi and will work too when it arrives sometime next year) and an Apple I-Pad, you can use the LCS App to make a control panel of your layout. Putting a ST icon on the LCS App display and setting it up to match the TMCC ID of the physical device will allow the app to track the location of locos on your layout in real time. The app will display the TMCC ID, direction, and name of each loco that passes over the ST.