Some jails do have the ability to allow the inmate to send texts from the jail to someone on their approved list.
Not all jails may be allowing inmates to text from jail but you could call up the jail where an inmate is housed at and ask if they do texting.
But even when the jail has texting devices for allowing inmates to text not every inmate will be allowed to send text messages back and forth to people outside of jail.
The texts are also closely monitored as well so do not text anything bad or try to do anything to smuggle anything into the jail for the inmate or help the inmate escape.
The jail staff who monitor the texts will find out and then you'll be in trouble.