"USB Detect" is only an automatic shortcut to your phone's settings and does not provide any additional features to your phone.
Most * Android phones can be used as a modem. It's called tethering and hotspot. When you use these features you can share internet ** to your PC and other Android phones and tablets.
In the phone's settings there is a menu that lets you do that either by using USB, Wi-Fi or Bluetooth or multiple at the same time.
If the internet sharing menu is available on your phone "USB Detect" will open it for you when you connect your phone to a PC *** or a charger depending on "USB Detect" settings.
* Some mobile carriers limit or block devices from being used as a modem unless you pay extra.
** Keep in mind that it is very easy to use lots of data when sharing internet to other devices and that it is up to you to find out how much it costs with your mobile carrier.
*** If a USB sensor is available on your phone it is available in "USB Detect".
Charger sensors are always available.
IMPORTANT!
Sharing internet to other devices might be in violation of your cellular service contract so check with your mobile carrier before you start sharing internet to other devices!
Many newer devices has some sort of battery saver feature. "USB Detect" must be excepted from this feature and be able to run in the background while the screen is off to work correct.
If the USB tethering option is greyed out even when the phone is connected to a PC the USB cable you're using does not support USB tethering. "USB Detect" can not work if the cable does not support USB tethering.
Official Android details about sharing a mobile connection by using tethering or hotspot on Android...
http://goo.gl/zg4tv
Support libraries updated
9Apps 4.9
