An Ontario, CA police officer was given a pager, paid for and provided by the Ontario Police Department. The officer apparently used the pager to text personal – and sexual – messages to his wife (who also worked for the police department). The wireless provider, at the request of the police chief, provided those messages to the police department.
The 9th Court of Appeal ruled that text messages are private, even when the employer provides and pays for those messages. (The Ontario PD even had a policy prohibiting personal use of the pagers).
For now – consult your employment attorney and don’t monitor your employees text messages.