I know this is a vacation home but generally speaking many, including the NIH and most state plumbing codes, want you to keep the temp at 140°F or slightly higher to avoid the risk of Legionella. It's considered safer to keep the temp in the water heater higher and use a temperature reducer or mixing valve at the point of use to avoid scalding. In studies electric water heaters were most susceptible to this when operated at reduced temperatures.
I have not seen any discussion of your situation which is not unique as I have no doubt there are thousands who do as you do with their vacation home water heaters. I know the convenience issue within the app is what you are worried about here, but I am suggesting that possibly the reduced temperature is more of a threat than you might have thought, and the problem with the app is minor in comparison.
"The optimal temperature for Legionella proliferation in water varies between 32°C and 35°C (89.6 - 95°F), but it can easily proliferate at temperatures of up to 45°C. Usually, there is no growth above 55°C, and a temperature of over 60°C (140°F) has a bactericidal effect. Thus, the WHO recommends that water be heated and stored at 60°C (3). However, studies in Quebec have shown, even when the thermostat is set at 60°C, a high percentage (approximately 40%) of electric water heaters remain contaminated because of the lower temperature, about 30°C to 40°C at the bottom of the tank. The probability of contamination will increase considerably if the temperature setting is lowered to 49°C. The risk of contamination is much lower for water heaters operating with fossil fuels, and is practically nonexistent for these heaters set at 60°C."
See the whole article from the National Institute of Health.