Things I have done in my apps.

FTSLink by Redpark

In the app the manifest enables USB attach and detach intents to be delivered.

* Asked for permission:

IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);			
this.parent.getParentContext().getApplicationContext().registerReceiver(mUsbReceiver, filter);

• ACTION_USB_ACCESSORY_ATTACHED re-starts the activity
• ACTION_USB_ACCESSORY_DETACHED is received in a BroadcastReceiver:

private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {

		public void onReceive(Context context, Intent intent) {
			String action = intent.getAction();
			Log.v(debugTag, "ACTION: " + action);
			if (action.equals(UsbManager.ACTION_USB_ACCESSORY_DETACHED)) {
				Log.v(debugTag, "Closing Accessory");
				closeAccessory();
			}

		}

	};

• Upon attach, connect to the Device

UsbAccessory[] accessories = mUSBManager.getAccessoryList();

            // There is only one USB, this must be the first one
            UsbAccessory accessory = (accessories == null ? null : accessories[0]);

            if (accessory != null) {
                Log.v(FTSLinkServer.debugTag, "Accessory found, try to connect....");
                RPUsbConnection connection = new RPUsbConnection(mUSBManager, accessory);
                ParcelFileDescriptor mFileDescriptor = usbManager.openAccessory(accessory);
                FileDescriptor fd = mFileDescriptor.getFileDescriptor();
                mInputStream = new FileInputStream(fd);
                mOutputStream = new FileOutputStream(fd);
                
                ... Create threads 
            }