As a relative newcomer to offshore sailing, I wrote a mobile app while we were sailing on our Atlantic Circuit. I saw an opportunity to improve our long-distance navigation, despite our onboard systems containing all the usual entirely adequate features.

It's very simple. It doesn't collect your data. It doesn't need you to sign in. It's free. It works on iPhones, iPads and Android phones and tablets, using the GPS in the devices themselves.

From moment to moment, particularly surfing joyfully in following seas in tradewinds, the instantaneous course of the boat varies a lot. This is accurately reflected on the instruments and the plotters, but what we really wanted to know was how we were doing on average over a longer period.

Maybe we just need a bigger boat, but that's a different story.

Our on-board tablet uses less power than our primary plotter. So if we can turn the plotter off for a while, can we get away with a mobile device that we can move around the boat with us?

We wanted to be able to mark our progress at any time, say at a watch change, or a sail change, and then check what the trend is in our journey. Have we sped up or have we slowed down?

Or maybe we just want to mark where we saw those dolphins.

All those log entries can be viewed in the app, or we can export them to a spreadsheet for use elsewhere.

We want a basic display that lets the skipper and the crew both know the same basic facts about our progress, without complication.

And also - have we detected any vessels on AIS recently? Offshore this can be a rare event. Sometimes we get a signal briefly and then lose it again, but we want to know it happened.

And finally, the endless breakfast discussion on board. Given all our progress to date, when are we likely to arrive at our destination?

We're still in the testing phase. Feel free to join in by filling in this form and I'll email you a link. We need a certain volume of testing before release. When we get through testing we'll make it publicly available on Android too.