I feel your pain I am in the process of designing a budget misting/watering system that I can control via smartphone for when I'm away from the house. None of the people I know have any appreciation for the hobby so I wouldn't really trust them to take care of my trees if I was away :/
I like the sprinkler idea, I had been imagining a slightly more complicated setup with basic smart plugs powering some small water pumps I have lying around, and some extra flex tubing I have as well. Controlling it would be easy, and all the water would go right into the pot via tubes. Since I have the materials it would be cheaper than new hoses and sprinklers but the downside is that it obviously wouldn't mist the foliage.I use battery operated timers, a hose and 2 lawn sprinklers. That is about as cheap as you can get. I wouldn't worry about being able to control it remotely which will add more expense.
I have 2 zones. One is watered every day and the other every other day. If you use proper bonsai soil you won't need to worry about the sprinklers going off even if it rains. It's practically impossible overwater bonsai soil. I often forget to delay my system when it rains. I've never had a problem with overwatering.
I'll burn a candle for whoever the patron saint of trees is.
Took a moment to look that up before bed last night. There's several others that seem to be asociated with gardening as well. I'm not even Catholic, but it seems like something I should look into.Saint Fiacre, an Irish Monk, is the Patron Saint of Gardeners