Create a Keyword in Textmarks. This will allow you to automatically generate participants in the challenge.
Sign up for a free account.
Select a Keyword of your choice
Create a message with information about the challenge
Select "automatically subscribe people who text in the keyword"
Publish the Keyword
Get the word out about your keyword. I created a blog post about the challenge that included how to text in the keyword. You can give it out to your students, post it in twitter, post it in Facebook...etc.
Decide on your topic for Picture on the Fly.
Remember the description (including where to send your mobile photo) needs to be no more than 140 characters for Textmarks.
Create a Flickr Account.
This is where all the participants will send their pictures.
Get the Flickr mobile address (you can do this by clicking on uploading tools--upload by email)Step 5:
Login to Textmarks.
Select ManageStep 6:
Click on Send Alerts.
Put in your information about the challenge (make sure you include the Flickr mobile address).
Click on Send.
Now all of your subscribers to the challenge will get the text message.
Set up a Slideshow.
You can set up a slideshow on your blog to automatically view the photos as they pop into Flickr.
I used Pictobrowser.
In Pictobrowser Click on Pictobuilder
Login to Flickr and Select your Set
Copy and Paste the Pictobrowser embed code to your webpage or blog.
The great thing about this challenge is that you can do multiple challenges using all the same information (no need to reinvent the wheel!).