Android application

What do you mean you need it to be a software base?

If you want a corporate Wifi mapper, I've used Acrylic WiFi heatmapper

https://www.acrylicwifi.com/

You can get it from there, it sits on a laptop and if you want to map correctly you need 2 wifi cards, a USB one works ok.

Regards
Alex

I see, is there any free ones i can use on the phone to check the wifi coverage

There are, however I would say that they aren't accurate, they aren't for business purposes, they can only connect to a very limited number of wireless boxes and they won't be able to give you a decent floor plan.

I tried to find a decent, free, corporate bit of software that would do it and they just weren't accurate enough.

Regards
Alex

There's no real wifi coverage app, as it's too difficult and requires special sensors and mapping.

You only have apps that show you the wifi signal strength.

Use those instead. For all corners in the room or building, note the strength, and "build" a map in  your mind, or roughly on paper.

Please note, no matter how advanced you're doing this, it's always a test at a point in time that may not be reliable in real world.

For instance, if you do this in an empty building, it will be distorted from reality if big metal cabinets still need to be installed.

Or if you do this during the weekend, when other surrounding (neighbors) wifi is not used, you may think you have a super stable signal (while during the office hours it might totally slump)

I have used WiFiAnalyzer from VREM (free for Android phones) with good success.  I don't doubt that the more professional tools do a significantly better job, but this has gotten me the answers that I need.

@Alex, If you followed OP's train of thought, the answer I gave is definitely a valid one. He wanted to use his phone, and wanted it for free. What I described will get a a very basic idea of a heat map he desires.

Saving someone some bucks on good ideas, is not the same as advising someone to not use a firewall (which clearly has other consequences).

@Alex:
Why are two WiFi cards needed?  The free app I use on my phone can connect to the AP and also show me the signal strength.

I'm not disagreeing, just trying to get better educated.

They were all helpful