Short answer: Yes.
You will need an iDevice to download and use the Stratus Horizon Pro app. Once the app connects with the Stratus3i, you will need to set the "Open ADSB" switch to on.
If anyone uses ForeFlight with your Stratus3, it will turn the Open ADSB switch off.
If you have ForeFlight, you can only use one or the other (FF vs iFly) with the Stratus3i
You will also need an iDevice and Stratus Horizon Pro to install any soft/firmware updates for the Stratus3i
Last time I did a firmware update, I needed to turn the Open ADSB switch back on.