The only thing that may indicate DOD activation would be the ScanGaugeII from
www.scangauge.com. It is designed to give live data to the driver about the engine performance...rpms, fuel rate, mps...and may be able to be programmed to show your DOD status. This is all speculation. My understanding is that the DOD function isn't necessarily on/off, rather it is a gradual process of stopping/starting fuel injection into the cylinders so that its operation is impreceptible to the driver, i.e., the amount of fuel injected is adjusted in(de)crementally.
From this, my guess would be that you'd have to monitor the fuel rates into each cylinder on the DOD system or the injector pulse widths and/or amplitude. Good luck!