Can I collect data from 5 different device with BLE from my Android phone? I have a custom made device something from https://mbientlab.com/ and I want to collect data from 5 of them through Bluetooth through android phone. Is it possible? I would greatly appreciate a link which shows how to do it? IS using PICONET for BLE is the solution? Is such an app already exist?
Since the app would be specific to the protocol the device uses to stream data, you need to talk to the manufacturer about this possibility. Since they advertise an "open source API" for communicating with the devices, it may be that they recommend you develop your own app to do this.

One thing to bear in mind is that the total amount of bandwidth available is not that huge. If you're simply collecting events (such as "the temperature went past a limit"), or if you're sampling data every few seconds, that should be fine (depending on the protocol they've used). If you want to collect (say) accelerometer readings 100 times a second, that might limit you to only one or two devices at a time, depending on what phone you're using to collect the data.