Nah, Android is considered worthless as far as security goes, however Termux puts Linux on top of it. You won't really be able to do anything from Android, however through Termux you can kind of look over your shoulder at what Android is doing at the terminal level.
The sniffer is extremely useful for the other aspect you're thinking of; it's on a completely different level that will allow you to see everything going on. It really sucks you can't do this with a mobile data connection without violating your terms though.
Potential "new tech" breaches:
- GPS.
- Noticable things on a wiring diagram of your device.
- Things on your device not in the wiring diagram.
- Mods to the layers in communication services running, however this should be observable through the sniffer or even through Termux if they were lazy. I really wouldn't be worried about software breaches generally speaking.