Android: How can I add a menu softkey to the standard softkey bar?

I'm developing an app and I'm having problems to make my menu accessible on devices with no menu hardkey.

I have found that the recommended solution for this is to use an ActionBbar. But I have started to develop this app quite a while ago and changing my TabActivity to an ActionBar results in an apparently endless chain of other problems.

I have found an app that adds a forth softkey as a menu softkey and my question is how can I achive this?

Here is what the softkey bar looks normaly:

https://docs.google.com/file/d/0B_dSVLmzXlwiaUhSelFVOXBvQWs/edit

Here is what I want to achive:

https://docs.google.com/file/d/0B_dSVLmzXlwiajdacW56cFdOb0E/edit

(Can't upload pictures yet because of my new membership)

That functionality is only available to remain backwards compatible and you really should try to implement this in an ActionBar. However, if you dont use the ActionBar and minSdkVersion is set to 10 or lower AND targetSdkVersion is under 14, you should get that extra button. From the android developers blog: http://android-developers.blogspot.com/2012/01/say-goodbye-to-menu-button.html