Or how about an app which automatically texts your significant other at random times during the day letting them know that you're thinking of them, but random enough that they won't realize that it's automated.
+1
I'd think that there would be an abilitiy to send pre-timed texts.
i.e. send to wife Text #1 at 9:48am
send Text #2 at 2:04pm
send Text #3 at 5:52 pm
(however, if there are lots of questions and answers in between, then text #2 may sound funny if it starts with, "since it's been a while...."