BluetoothQueue is a sample app for Android that demonstrates the idea of a queue system for BLE commands.

Read more about it at blog post here:

http://www.brendanwhelan.net/2015/bluetooth-command-queuing-for-android

The app requires Android device with OS 4.3 or greater.

The app also assumes the device you connect to has a standard Serial Number characteristic in a Device Information service.

https://developer.bluetooth.org/gatt/services/Pages/ServiceViewer.aspx?u=org.bluetooth.service.device_information.xml