I use this code to let my C# wx.App run in foreground on Mac OS X - no packaging/bundling of the main exe needed:
IntPtr psn = new IntPtr(0);
Monobjc.Cocoa.AppKitFramework.TransformProcessType(ref psn, ProcessApplicationTransformState.kProcessTransformToForegroundApplication);
The bad thing here is that you obviously have to add Monobjc to you project. But as this project itself is open source, maybe copying only the code for this functionality does the job.
I'd really like to see this to be added to the code of wx.App.