BMV080 is a low-power, low-cost PM1, PM2.5, and PM10 sensor module with I2C and SPI interfaces that sells for just $29.90.
In this video I'm building an Arduino Heart Rate Monitor that is housed in a toy handle in the style of the Star Trek Tricoder. The device uses the PulseSensor with an Arduino Pro Mini and an OLED ...
If you're savvy and want to do a bit more home monitoring, these interesting sensor ideas might be worth trying.