Completing HTTP POST request when wireless network connects
You could do this using onx.ms. You'll need to know a bit of scripting, but it's not that hard. onx.ms is basically an automation tool much like Tasker.

onx.ms has the ability to automatically run the script you made at specific triggers (like Wi-Fi on/off). These triggers itself are to be defined within the script you make.

Have a look at this for the HTTPClient object you can use in the script to make this happen.

Though not a perfect app as it requires some internet action initially I presume and the fact that you'll need to have a facebook account to use it. But the whole javascript like scripting and not-so-bad documentation, makes it more fun to use.