You can use your SegmentedControl name .Value to get/set ones.
SegmentedControl1.Value
Also with Xojo you have iOS sample (example) called SegmentedControlExample under iOS - Control of Examples TAB under New Project Dialog.
Also you can use this as well (this is just example code)
Dim Ret As Boolean
’ Get Selected (True/False) value
Ret = Self.SegmentedControl1.Item(0).Selected
If Ret = True Then
System.DebugLog(“Item 0 is selected.”)
Else
System.DebugLog(“Item 0 is not selected.”)
End If
System.DebugLog will printout string expression in debug log of terminal/simulator which you can see/view from Simulator, menu DEBUG then Open System Log…