If I understand you correctly you would like to have a device with microphone to show you numeric value of your voice frequency? This is pointless distraction. Focus on the vibration and feel how it resonates inside your body and how it carries energy. Train with simple vowels like A, I, O, changing tone of your voice to get a feel which tone or key gives most powerful vibration. Get a feel how different keys of the same vowel and different vowels vibrate in different parts of your body and how it changes depending on how much air you have left in your lungs. Give your vocal cords some time to adapt to this new work.