...If you're asking whether they can follow your emails and texts "live," the answer is no.  However, cops can get a judge to issue a subpoena for the texts and emails if they can show that the texts and emails are relevant to an investigation.

In order to wiretap a phone, cops need a warrant.  A warrant requires more proof than a subpoena; it requires a showing of  "probable cause" of a crime.

Another difference between emails/texts and phone calls is that there are records of emails and texts.  Barring exigent circumstances, there is no immediate need to "monitor"  them as there is with telephone calls.  The records can be obtained later; phone calls are ephemeral.