I agree with Jeff, nobody is saying you should withdraw the proposal. This is just discussion to evaluate as most likely no one of us did actually test the code. (I'm going to order a ultrasonic-sensor to do so as they are pretty cheap). In fact I like this feature and would integrate it with perl-firmata and the perl-based house-automation software http://fhem.de that I use. If this requires a partial rewrite of NewPing-library to make it nonblocking, then why not? This wouldn't mean you'd be forced to maintain this for an extended period of time. It just means it might take a few days longer to integrate with configurable-firmata.