This came up at a couple of recent The Blank Screen workshops: how to send tweets or Facebook messages when you’re not around. Both times it came up, it was evil people who’d just learnt I start work at 5am and they wanted to send me a tweet to check. But weren’t so keen or so evil that they wanted to be up at that time.
If you have nicer reasons to do it, try one of these two possibilities:
Free for personal use hootsuite.com
Log in once to Twitter, Facebook, Google+, LinkedIn and/or Foursquare and write a message for it to send to any or all of them whenever you tell it to.
I use Buffer for my personal Self Distract blogs that I write and publish on Friday mornings. The first tweet is live but then I always intend to send another one around lunchtime. And then that evening. And a last one the following Monday. Buffer lets me write the lot one after another and know that it is being sent for me at the time I say.
I do this because I regularly forget to send the tweets live. Now I regularly forget that they are going to be sent live and I suddenly get a unexpected notifications of retweets from the various tweets Buffer has sent for me.