No, only Android. Really simple though, so wouldn't take much to put together for the iPhone.
Note that the postcode doesn't really offer much as it's a known constant for any premises. Since you're having to give the patrol a seed value, you may as well give them a unique code for the site and leave the postcode part out. The app doesn't offer any level of security in the equation.
It would be better if it were a password that the security patrol were given as their constant. The password + seed would then provide the code. That way, the seed values and passwords are of no use to the holding parties unless combined. If your patrol password becomes compromised, you generate a new one and the seed changes accordingly.