It sounds like you already have an awesome helper, but your system might be more complicated than it needs to be. Why can't you put the drip on a timer, with the water turned on by solenoid valve? And maybe you could add some sprayers on a valve to overhead water the potted plants, that you'd only turn on when you're going to be away. Not as good as hand watering, but I bet you could make it work. The heat, could you not put it on some sort of smart controller that you can monitor on your phone? Or a smart thermometer to alert you when there's an issue? Regarding your sister not recognizing if there's an issue, other than underwatering, what issue could she need to recognize if we're talking about a few weeks? As long as my plants are getting watered, there's not too much that could happen in a few weeks of me being gone. You could even put cameras in, so you could check remotely for issues.
The way you describe it, like a toddler, needing constant supervision, it sounds like you may be in an abusive relationship with your plants. Somewhat joking, but somewhat serious. And if you are injured and off your feet for weeks or months, how much time each day will it take your family to take care of things, and will you be jeopardizing your recovery trying to move around in there doing things yourself when you should be in bed? I'm sorry to get so serious, but I think anything you can do now to make it more on autopilot is worth doing.
Personally, I just don't leave for more than a few days in the summer, or a week in the winter. I know it's a labor of love for me, but I can't expect other people to care. Last couple trips I went on I came back to plants looking like they would've died if I'd been a few hours longer. But once I get a permanent place, I hope to get things automated like I preach.
$50 doesn't sound bad, for two 30 minute visits. If it takes 15 minutes to get there, that's two hours total. And that gas costs money, etc.
And Ryan, I love that your friend is named Oatmeal. It'd be awesome if he found a girl named Raisin.