Ok.. using smart phones as recording devices is certainly economical and feasible.
There are plenty of recording apps to investigate, some require more up to date phone's with more powerful processors / memory.
But audio quality is mostly let down by the phone's poor inbuilt mic.
Recent iphones actually have fairly acceptable inbuilt mics though you obviously pay a higher premium

However there are recent developments in accessory devices that allow good quality dynamic XLR mics
to be plugged into the headphone socket of some Android phones.
For less than 30 quid this mono entry level adapter, Saramonic SmartRig Microphone Pre Amplifier Audio Adaptor
is becoming popular, and gaining enthusiastic user reviews / youtube videos...

I bought one very cheap last month in an Amazon sale,
but can't remember where I put it, so have not used it yet.
Therefore, can't report how well it works with any of our Android phones [or tablets].
Oh well it'll turn up when I'm looking for something else...

Btw, Amazon are also occasionally doing lightning sales on the more advanced and expensive models in the Saramonic adapter range.