Army Oil Analysis Program, AOAP. Used for periodic monitoring of wear metals, fuel dilution, soot load and lubrication value. Saved a lot of oil, samples were initially drawn using a Vamp Gun (vacuum pump with disposable straws, sucked oil from dipstick hole directly), then valves made this far easier.
Yes, it is under system pressure.
Yes, it is suitable for turbocharger lubrication. You still have to find a suitable return line which should be 3 times the diameter of the supply line.