There is a simple app I made for iPhones that keeps a record of all your aircraft and their average flight times which when started, sounds an alarm when it is time for you to land. You'll notice on the AppStore About screenshots that Radical RC Wright Flyer B is shown as an example aircraft. I couldn't resist and this gives up more exposure.
* You have to enter a Make, Model and a duration that is greater than 00:00.
* Swipe an aircraft in the list to delete it. I provide a Sample Aircraft for you, you can delete it or edit it.
* Click the '+' button on the main screen to add your aircraft.
* Tap an aircraft from the main screen and click START to begin counting down. Turn up your volume to desired level.
* There are Ads on the bottom of the screen but it's FREE.
It's just a simple app but handy in the field in case your TX beeper is not loud enough. It's handy for listing all your aircraft too. You can even take a picture of your aircraft too. Of course it's FREE which is a nice touch. It's called RC Clock or link is below. I fixed a bug that made it crash if you didn't take a pic. It works now.
Here's the link to it: