How about a Zigbee device. I've been using the firmware at PTVO on a TI CC2530 board purchased on ebay CC2530 board. This one was $5 but I've seen the a few dollars higher as well. The only issue folks might have is soldering to the 0.050 pitch contacts.
So far I've put together:
- digital input
- BME280 Input
- digital outputs
- Analog inputs
I have information on how to program this board using a NodeMCU (see Haas Thingshield thread). I have designed a small carrier board with some filtering for Analog input, 5V to 3.3V and some leds. See further down in the above Haas link.
If anyone is interested I can provide more information..
