Correct in the fact that the ST-16 gives a total battery voltage. The battery is a 4s, which means that there are 4 cells in the battery.
To my knowledge, all cell voltage alarms do not monitor each cell, but they sound out an alarm when the cell voltage gets down to around 3.7v (depending on the brand).
3.7v X 4 is 14.8v. Wouldn't it be better to just monitor your battery read-out on the ST-16 and make sure you land prior to that level, rather than rely on something additional like a cell voltage alarm?