How to restrict the GadgetTrak App from being deleted from my iOS device?

You can set you iOS device to require the Passcode in order to delete an app. That way, a thief can not simply delete the GadgetTrak app from the device. They would need to know the owner's Passcode.

You enable this feature from your device's "Restrictions" settings. Locate these settings by tapping:
Settings > General > Restrictions

Turning on Restrictions:
To Enable Restrictions, tap Enable Restrictions and enter a passcode. The passcode will be required to make changes to these settings.

Turning off Deleting Apps:
Scroll down to find the "Deleting Apps" and turn to "Off"

Setting an item to "Off" means it will prevent that action, while setting to "On" means that it will be allowed. By default when you first turn Restrictions to on, all actions are allowed, and all setting will most likely be set to "On".