I believe smcfancontrol installs its kext by demand from inside the Cocoa App. I don't know how it's done (I only do UNIX stuff on my Mac =/) but I believe it changes the .kext owner and invokes kextload. You can 'sudo' from inside a Cocoa App by using AuthorizationExecuteWithPrivileges:
About PKGs: I think that they're okay, but, historically, they're maligned for being "black boxes" that install files all over your system. App files, OTOH, are (99% of the time) clean, live on /Applications, and sometimes use ~/Library.
http://michaelobrien.info/blog/2009/07/authorizationexecutew...
About PKGs: I think that they're okay, but, historically, they're maligned for being "black boxes" that install files all over your system. App files, OTOH, are (99% of the time) clean, live on /Applications, and sometimes use ~/Library.