So Android devices must support USB host / USB OTG to connect to the PM monitor via a USB OTG cable.
What this means is that the USB port in the Android device must be able to send 5V of current to make a connection to the C2 PM3/4.
Some devices have this disabled due to the manufacturers being worried about the port sending power out. It is simply a diver file in the Android OS that allows it to work or not so updates to devices can deactivate USB OTG.
If the port is of a cheaper quality such as you would find in most sub £100 mobile phone it will not send sufficient current out so can never support USB OTG.
Here is a list of supported devices from the C2 website -
Asus Infinity Tablet Yes
Droid Razr M Yes
Google Nexus 7 (2012 version) Yes
Google Nexus 7 (2013 version) Yes
Google Nexus/Verizon Yes
HTC DNA Yes
HTC One (Android 4.2.2) Yes
Motorola Rzr Maxx HD Yes
Nexus 6 Yes
Samsung Galaxy 4 Yes
Samsung Galaxy S5 Yes
Sony Xperia GO 4.1 Yes
Sony Experia z5 Yes
I was hoping people could add to this list by posting here if they are using an Android device connected to a PM3/4 with a USB cable.
I know for sure that the Alcatel Pixi 4 (4) does not work, or at least doesn't work without some serious IT magic.
I am currently looking at the Lenovo Tab 3 Essential 7inch, a number of online sources say it supports USB OTG, it is difficult to take the plunge without knowing for sure. At £50 it is around the least expensive Android device I have found that may be able to support linking to the PM3/4, also almost same price as the iPhone connect cable and lightning adaptor.