Do you mean the keuwl site?
https://www.keuwl.com/Metronome/
It works for me
https://play.google.com/store/apps/details?id=com.keuwl.metronome
I also use other of their handy applications, like WiFi Analyzer, SPL Meter, Spectrum Analyzer, Function Generator, Pulse Echo Meter, Spirit Level, Compass, Protractor...
I mean this:
http://eumlab.com/pro-metronome/
Also the site root. Everything I tried there gives there same Django error:
AttributeError at /pro-metronome/
'NoneType' object has no attribute 'groups'
Request Method: GET
Request URL: http://eumlab.com,eumlab.com/pro-metronome/
Django Version: 1.8
Exception Type: AttributeError
Exception Value:
'NoneType' object has no attribute 'groups'
Exception Location: /home/wwwroot/eumlab/mainweb/context_processors.py in mobile, line 19
Python Executable: /usr/bin/python
Python Version: 2.7.17
Python Path:
['/home/wwwroot/eumlab',
'/usr/lib/python2.7',
'/usr/lib/python2.7/plat-x86_64-linux-gnu',
'/usr/lib/python2.7/lib-tk',
'/usr/lib/python2.7/lib-old',
'/usr/lib/python2.7/lib-dynload',
'/usr/local/lib/python2.7/dist-packages',
'/usr/lib/python2.7/dist-packages']
Server time: Thu, 9 Sep 2021 04:17:52 -0500...
Lots more similar.