Earlier this year we reviewed a unique new carbon monoxide detector, the Aithre Shield, that used a free app to offer precise monitoring of the cockpit environment. Now the company has added oxygen system monitoring to the mix, with an updated app and a new accessory called Altus.

The Altus plugs into a portable oxygen bottle using a high-pressure T-fitting, then the device attaches to the side of the bottle with a velcro strap. It’s completely portable and your existing pressure gauge is unaffected, so after the initial setup there’s really nothing to do. Once Altus is connected, you can mount your oxygen tank out of the way – many pilots like to strap it to the back of a seat. It’s powered by 4 AA batteries, which should last for months under normal use.

But how do you know how much oxygen is left if the bottle is behind your seat? Instead of having to crane your neck to see the small gauge on the oxygen bottle, the Altus sends that information wirelessly to your phone or tablet for easy monitoring.

Using the free Aithre Connect app, you can get a real-time look at your tank pressure (updated every 6 seconds, and accurate to 10 psi). The app also shows a 15-minute graph of tank pressure, so you can track the trend, and it continuously calculates flow rate and time remaining. That last feature is simple, but the most useful – in a busy cockpit, what you really want to know is how long you have left in the tank.

More than just a remote gauge, the app can also provide Siri voice notifications if you pair your phone to a Bluetooth-enabled headset. This is a great way to keep track of your oxygen status without burying your head in the cockpit. The app will warn when tank pressure drops below 500 psi, and an onboard pressure altitude sensor provides alerts when you reach critical altitudes for oxygen use (i.e., 12,500 feet). It also allows you to set custom alerts for other altitudes if you’d like (10,000 feet at night is a rule some pilots obey).

Setup is a breeze: just turn on Altus and open up the Aithre app. Connection is essentially automatic, so there’s no need to go into the Settings app and mess with Bluetooth settings. If you’re using the Aithre Shield CO detector, you can swipe left or right to go back and forth between the two sensors.

The Altus Oxygen Monitor is available for $350, and includes a velcro band, quick-disconnect sensor, and a T-fitting (typical on the popular line of SkyOx systems). The Aithre Connect app is free to download in the App Store.