Hi, I'm the owner and only developer. Your image data is sent through a TURN server I operate on AWS in order to facilitate the remote viewing, and only if a synchronized device exists and is online. You don't need have to synchronize an iOS device to use the other desktop features. Aside from the TURN server, the app makes connections to another server I control for managing synchronization between devices.

The data is encrypted using two way TLS and the traffic is sent (without any processing or storing, or transmitting to third parties) to devices you have synchronized.

Your fear is probably not atypical, and as an indie dev it's maybe my biggest obstacle for this app's success. With that said, my number one priority for users is data security. I spent a great deal of time working on the security aspects alone, and if you have any questions about the details please feel free to contact me-- my information is available on the website linked.

EDIT: more clarity (I hope)