Hot water heater timer app? With countdown timer?

[JDRoberts]

Welcome! I suspect the switch control functionality exists, but customizing the display may be the trickiest part!

First, start exploring the apps that already exist. The Power Allowance smartapp, for example, is popular for on-demand water heaters and other devices that you run for a fixed period of time.

List of all Officially Published Apps from the MORE category of Smart Setup in the Mobile App [deprecated]

The following is current as of Sept 9, 2015. This is a list of the officially approved SmartApps that are available for installation through the SmartThings mobile app under the SmartApps tab. In each category, you will find a combination of community contributed & SmartThings developed SmartApps. To install any of these, open the mobile app, select the Marketplace icon ([image]), and select the SmartApps tab. SmartThings Recommends Smart Lights by SmartThings Control and automate Lights and Switches. Safety & Security Notify Me When by SmartThings Receive notifications when anything happens in your home. Enhanced Auto Lock Door by Arnaud Automatically locks a specific door after X minutes when closed and unlocks it when open after X seconds. Severe Weather Alert by SmartT…

Next, get an overview of the many scheduling options available:

A Short Intro to Scheduling/Device Control/Rules in SmartThings Classic

(March 2018: All of the following applies only to the SmartThings Classic app. If you purchased your hub after March 1, 2018 and are using the new “SmartThings (Samsung Connect)” app, creating rules works differently.) You’ve got your hub. You’ve got some devices. Now how do you schedule what happens when? SmartThings doesn’t have a rules engine/scheduler, so there’s no one tutorial for how to do this. But it’s an open platform, and there are about 12 different ways to set up various kinds of schedules. Some require custom code, some don’t. A “scheduler” in this context is anything that causes a networked device to perform an action, even if it’s just to toggle on or off immediately. (Network engineering definition, forgive me. ) (Note: as of April 2017, the original author of …

Once you’ve gotten a feel for all that, if you decide you’re going to need help with something that doesn’t already exist, there’s a topic for that–it’s listed near the end of the scheduler FAQ.