You can enable/disable any of your contacts using the mobile app.
Tap on Contacts in the menu.
Tap the toggle to turn off/on any of the contacts.
Enabling/Disabling Alert Rules
Though you cannot edit your alert rules in the mobile app (for that you need to login to desktop version of Monitis), you can enable/disable them.
In the Contacts view, tap on the Alert Rules under the contact that you want to enable/disable alert rules for.
Alert rules for the contact will be shown. Toggle on/off the alert rule you wish to enable/disable.