Is there a way to toggle wifi on and off programmatically in iOS?

It's definitely not possible to turn WiFi off or on with any public (documented) API.

It might be possible to achieve this even on a non-jailbroken device using private functions.

See Apple80211Functions - there is a private function called Apple80211SetPower which is a good candidate for this job. But using it would be also interfering with automatic TX power settings - could result in either increased battery usage or decreased WiFi link quality (or both).

Of course your app would most definitely not pass App Store approval using this.

You can see how Apple80211 functions can be used if you download Stumbler source.

Stumbler SVN checkout is done by:

svn checkout http://iphone-wireless.googlecode.com/svn/trunk/ iphone-wireless-read-only

There are also two other projects that might help you start with low-level WiFi functions:

web-login-helper

BECHA

I'm fairly certain that the SDK does not allow access to turning Wifi on or off using the public framework, sorry. You could use a private framework but then you won't get your app past Apple, I suspect.