pp. Sending text messages while standing outside on a smoking break.
Other Forms
The smoking ban has had an unusual side effect.

A record number of text messages have been sent by smokers who want to pass the time over a cigarette while banished to outside venues. …

Experts have now dubbed the phenomenon 'smexting'.
—Mark Prigg, “Smoking ban leads to surge in texting,” The Evening Standard, August 07, 2007
It's August — and therefore silly season for the British press who, in the desperate desire to drum up an interesting story, are looking around for something that sounds vaguely plausible and fun.

Hence the arrival of a new "trend" for "smexting": an increased number of text messages being sent because smokers (now forced to hang outside since the adoption of a smoking ban in England on July 1) are spending their time tapping away on their mobile phones.
—Bobbie Johnson, “What the hell is smexting?,” The Guardian, August 06, 2007
2007 (earliest)
In the two weeks following the smoking ban, texting across Orange's network of 17 million mobile phone users shot up by 7.5million texts, leading Orange to dub the trend 'smexting'.
—“Smokers Turn To Their Phones As They’re Sent Outside,” Orange Mobile, August 05, 2007