The Womb Music Belly Speaker System works using a 3.5 mm audio jack which is fairly common in most devices. So if your device has a 3.5 mm headphone jack or audio-out jack then purchasing the Speaker Pack version of our product should work fine for you.But what we see in the cell phone industry especially is that manufactures of cell phones are removing the headphone jack and opting towards wireless solutions like Bluetooth. Because of that we developed the Womb Music Belly Speaker system to also work with our Bluetooth Controller. This allows you to connect the speaker to the controller and then sync your phone to the controller. The best way to get the Speaker and the Controller is to purchase the Deluxe Pack, which has everything.Another advantage of using our Bluetooth Controller is that you have an infinite range of volume control for BOTH the Baby and for You! By using the controller you can set the volume that you like and then on the belly speaker cord, you can turn down the volume for the baby.As technology continues to evolve we expect "most" cell phones to loose their 3.5 mm headphone jack. This is now true of all Apple products and some of the new Android products. Because of this trend we've had many customers come to us for just the Bluetooth Controller to use with either their previously purchased Womb Music Belly Speaker or a competitors product like Belly Buds which don't work with most modern phones. If you find yourself in this situation, you could purchase our Womb Music Bluetooth Controller and use it with your previously purchased Belly Speaker, regardless of who made it. To do this we'd recommend that you purchase the Controller Pack which would provide you just the controller, and not the speaker.So here's the summary:Deluxe Pack - Includes the Bluetooth Controller and the Speaker - Best Value!Speaker Pack - Includes just the SpeakerController Pack - Includes just the Bluetooth Controller