Both.
You can link with Gollum using an Android/iOS smartphone with Bluetooth Smart feature.
In some cases, you will need a higher throughput than what BLE can offer, so you will have to use Gollum using its USB port.
You can connect Gollum to an Android Smartphone with USB Host mode (USB host mode is supported in Android 3.1 and higher) using a USB micro Male/Male cable.
You can also connect Gollum to a computer (Linux) and use #rfcat Python scripts or our native C stack to send/receive data.