I’ve been really into the nRF52832 lately, a newer chip from the same company as the nRF24LE1 mentioned in the article. It has BLE, and you can find dev boards with all of the IO pins exposed for $5 (sometimes $2.50 on sale) on AliExpress, or impossibly tiny ones with chip antennas (six fit on a dime!) for closer to $15.

I just realized that the ones I have sitting around have roughly 64x the RAM, 32x the storage, and are (VERY roughly, I had trouble finding compatible numbers) 2,000 times as powerful processors. There’s so much more they could be doing!