Android: Starting An Activity For A Different Third Party App

Yes, it's possible but you need to know the correct component name. Launch the last.fm app regularly and check the logfile for the cmp=... information that's been used when the app is started. Use this as well in your app then.

I start the Z-DeviceTest app from the market from within my app without a problem like this:

final Intent intentDeviceTest = new Intent("android.intent.action.MAIN");                
intentDeviceTest.setComponent(new  ComponentName("zausan.zdevicetest","zausan.zdevicetest.zdevicetest"));
startActivity(intentDeviceTest);

in my case the info I took from the logcat was:

// dat=content://applications/applications/zausan.zdevicetest/zausan.zdevicetest.zdevicetest

// cmp=zausan.zdevicetest/.zdevicetest

in order to know how to start the app with the right component/class... do the same for the last.fm app

Edit: I've tested to launch Last.fm from my own app, and this works fine without any errors:

final Intent intentDeviceTest = new Intent("android.intent.action.MAIN");                
intentDeviceTest.setComponent(new ComponentName("fm.last.android","fm.last.android.LastFm"));
startActivity(intentDeviceTest);