I definitely prefer the app over a key fob for security purposes. However, if you want to use a key fob with 2GIG there are a couple programming options that can help.
In the RF KEY FOB PROGRAMMING STEPS section on page 39: Select Fob (3) key 2 can disarm (0-1). Disabling this is highly recommended if you’re going to leave the key fob lying around the house or mounted on the wall, so it can’t be used to disarm.
In the CONTROL PANEL PROGRAMMING QUESTIONS section on page 53: Q-73 Select disarming keyfob after alarm (alert) (0-1). This says that if you enter with a keyfob and disarm but the alarm has already sounded (someone might be in the house) it alerts you with 4 beeps, telling you to proceed with caution or get out.
Key fobs are meant to be carried on your person, not left lying in the house. Leaving a keyfob in the house without disabling disarming on that fob is a security vulnerability.