I use an iPhone app called "Alarms" from Yoctoville. Its alarms show up on my Apple Watch, unless I have my iPhone open.
The in-app purchase gives you "Nag-Me", "Repeat", and "DayMinder" features.
In my case I have a "Repeat" for Everyday starting at a specific hour.
At the beginning of the "Repeat" event, I have a "DayMinder" that goes off every hour, for 'n' hours.
I have a "Nag-Me" for 3 times every 15 minutes per "DayMinder" event.
So in my case, I have a "Stand Up" notice every day, once an hour, but if I do not dismiss the "DayMinder" event, it will "Nag-Me" every 15 minutes until it is time for the next hourly "DayMinder".
I am just trying to make sure I stand once an hour starting at the top of the hour, and not in the last 15 minutes.
The "DayMinder" can be set in minute increments, so you can have it set for 20 minutes, with a more aggressive "Nag-Me", like once a minute, to get yourself in motion.
I have found "Alarmed" to be very handy. And at least on the iPhone, it allows for different alarm sounds, so for things like "get the group together for lunch" or "get ready to go home" alarms, I have a soft "Ding". For" GET UP and TAKE THE TRASH OUT!" I have a much MUCH more annoying alarm sound. And I reserve some sounds for specific kinds of events (when I say reserve, I mean I only try to assign that sound for specific type of events; the software does not enforce sound assignments).
Besides scheduling alarms, it has Timers, and you can create preset timer duration's, the alarm sound, and if it repeats, nags, etc...
And it has a Geo-Location alarm, where it can trigger an alarm you associate with a location, such as you need to run into the grocery store on your way home, you can set a Geo-Location Alarm to go off as you are passing the grocery store.