Not many mariners realize that the most accurate barometer on the boat might be in their pocket… in their cellphones. There are not any native functions in iOS or Android phones that show the pressure reading, so you would not know it is there by just surfing around the functions of your phone.  It is not listed anywhere.  A third party app is needed to test that you have one.  There are many free versions of such apps, which brings up point one. Why do we make another one when there are so many already?
We want to let folks know about this tremendous resource, but then we are asked for an app recommendation, and the problem begins. Until now, the apps have all been too complicated. They want to do more, so they end up doing things like getting your elevation from the GPS, which even with a WAAS satellite connected is not accurate enough for barometer work adaptable to marine navigation.  In these days of remarkable weather services via model forecasts, we want the pressure accurate enough that we can tell if a surface analysis map is correct or not, so we can believe the forecast. In the tropics, we can also use accurate values of the pressure as a very powerful means of tropical storm forecasting.
Even worse than that, some apps get what is often called a “reference pressure” from the nearest airport, which are readily available online. Again, these maneuvers end up with pressures that are not accurate enough for our needs. There are even a few Andorid apps I have seen that do this without even saying what they are doing  In short, we could not find any app that we could recommend to our students to take advantage of this powerful, free resource.
Also only a few of the apps include a way to offset the sensor pressure, which, as good as the phone barometers are, they do, almost all, need some small adjustment (up to ± 2 mb or so) to be set right. So having an easy, transparent way to do that precisely is crucial.
Then the other common drawback is most apps do not have a way to store the data at all, let alone storing it with the time and location that we need.
So we have addressed these issues in the Starpath Marine Barometer App for iOS and Android.