Does pitch monitor apps really help?

I've installed an app that monitors the pitch of the audio input, so for example when I say a note it says which note it is. Just wanted to know if anyone here have made this and if it's a good way to gain pitch control (I've been trying to sing the same note over and over looking at the monitor so I know when I change it unintentionally), or if I should just use a piano (I don't have one, but tried using a piano app and it was really hard for me to say if I was really singing the same note that I was playing). Any other tips on improving my pitch accuracy (I realized it's really poor so I want to improve it before trying to learn other things)?