Hello,
im kind of lost, i need to install a distance sensor buried in a well of water, and will need a lot of tweaking and reprogramming until i get the desired correct measurements.
so i need OTA, extremely low power (battery powered, sleeps most of time), so i went to ultrasonic sensor HC04 which is even powered through GPIO of pro mini, and an nrf24l01+. the main problem is OTA. My concerns are:

1. should i burn MYSBOOTLOADER on sensor and Serial GW ?
2. if bootlader burnt, any sketch can do the OTA?
3. should I use only MySensors GW SW, or can i have my own sketch.
   Any ideas are welcome.
   Thanks a lot

hello,
i know it is late, but others could see it too.
i had the same problem running small (LOW POWER) modules on power banks, because the battery or power bank has a built in power meter, while it is charging and consuming power, there will be power on the USB port, but the arduino's consumption is very tiny regarding charging a phone. you need to disable this feature somehow.