Jongla CEO Riku Salminen

A smart and nice guy with great practical advice for devs http://www.telco-ott.com/opinions/2014/05/qa-riku-salminen-ceo-of-jongla/

Jonga is ultralight butbheavy in features https://play.google.com/store/apps/details?id=org.apache.android.xmpp&hl=en

Very cool free chat app.  5 / 5 imo.