What are /r/sightsinging's favorite Products & Services?

From 3.5 billion Reddit comments

I think this: "Vocal Pitch Monitor" android app is absolutely excellent for this:

https://play.google.com/store/apps/details?id=com.tadaoyamaoka.vocalpitchmonitor

Buy the ad-free version, it's excellent and about £1.50.

I found that patiently figuring out what melodies sound like, and only then checking that you've got it right with the app is a great way to learn, but if you need to work something out fast then whistling or singing into the app really helps.

On the other hand, listening to recordings or playing things on instruments seemed to really harm the learning process.

Thanks very much for your reply and also for your previous post on how you learned to sight sing.

I have downloaded the app you recommend in its Kindle Fire version (I think tbis might be a stripped down version; I don't have an android or apple device) https://www.amazon.co.uk/Tadao-Yamaoka-Vocal-Pitch-Monitor/dp/B0185TIYN2/ref=sr_1_4?s=mobile-apps&ie=UTF8&qid=1536152742&sr=1-4&keywords=pitch

I'm being dense, but please could you talk me through how you use this to check your sight singing? Why do you find this a better technique than listening to recordings?

Thanks again.