The timing model strategy discussed in "Profit With ETFs" by Gerald and Trent Gardner is available to download here.
Once downloaded, from within the NinjaTrader Control Center window, select the menu File > Utilities > Import NinjaScript and select the downloaded file. This strategy is for NinjaTrader Version 6.5 or greater.
You can review the strategy source code by selecting the menu Tools > Edit NinjaScript > Strategy from within the NinjaTrader Control Center window and selecting TimingModel.