Wireless brewing temperature sensor

Hmm. Sounds good - next step is trying to control the temperature, any maybe counting bubbles :)

• DS18B20 sensors say they're waterproof. If you used a grommit (or glue) and pushed only the stainless steel bit into the beer you could be pretty sure it was sterile too.
  
• Espruino should manage that easily on an old phone battery. Even on a 700mAh from an old Nokia (Galaxy S3 is ~2000mAh) battery it'll run in sleep mode for 6 months. Just use setDeepSleep(1) and only wake the radio up when you need it.
  
• It depends - you might be able to find a USB NRF dongle. I'm not sure which Linux computers have SPI - but a Raspberry Pi or some OpenWRT device would have it. If you had a bit of time, it'd be awesome if you could implement the SPI on Linux for Espruino (shouldn't be hard - it's just file IO), and then you could run Espruino on your PC and use the same NRF24 drivers :)
  
  

Hope that helps - happy brewing :)