I used this a lot when I was in New York City this summer. The CityMapper app, It REALLY helped me on the bus.
It worked perfectly on the bus at first but after a while it took it a second to realise I was at my stop so it only ended up telling me I passed my stop. (it would buzz pretty much the second the bus left my stop) so I had to be looking and paying much attention, which I didn't mind. After all, I was trying to get where I was going so it was my business to have a heads up and it was usually only ever one stop off.
I could tell the moment I passed it so I could orient myself to go back one stop as in the time that I missed my stop it was only a short distance behind me.
Since I can't see the street signs, I loved using this because it told me every stop between my stop and where I started and I could look when I passed it. I wasn't really able to read them but it helped me feel more secure knowing I could explain where I was if I needed to so do.
I didn't get a chance to try it on the train except once but I couldn't use it because I got no service underground.
I had a lot of trouble with it walking though..I had to play around with it but ended up just relying on a friend using google maps and trying to use google maps myself. That part was a bit frustrating, the walking bit. Mainly because I was so not used to using it.
Definitely my favourite travel app so far though really I haven't tried many of them. Citymapper also allows you to make a profile within the app and even change cities in the app if you travel from one major city to another which is really encouraging and just feeds my sense of adventure even with a visual impairment. It made me feel a lot more secure and continues to be available in many of the major U.S. cities. Even major countries too I believe.
I look forward to getting to know the train system better with it when I travel again.