Set it down.
The app records every night on its own. It reads how your phone moves and keeps a 30-second summary.

While you sleep, your phone lies still. NightStand reads that stillness as your night.
How much the phone moved
The night it measures
The phone lay still from 11:00 PM to 5:41 AM and was picked up twice. You guessed 7h 15m, 41 min more than measured.
The app records every night on its own. It reads how your phone moves and keeps a 30-second summary.

Each morning, it asks about your night before it shows the measurement: how you slept, when you fell asleep and for how long.

One 30-second test in the morning check-in and one before bed. Five more tests of attention and memory, any time.

Your guess beside the measured night, on one clock, with each time you picked the phone up.

Six 30-second tests of alertness, memory and focus. Trends set each score against the night before.
Alertness
A counter starts at random moments. Tap as fast as you can when it starts.
Processing speed
A symbol appears in the middle. Tap its number from the key at the top.
Working memory
Letters appear one at a time. Tap Match when a letter is the same as the one two letters before.
Impulse control
Tap as soon as the green circle appears, and hold back on the pink square.
Memory span
Pads light up in a sequence. Tap them in the same order. Each round adds one.
Focus
A color word appears. Tap the color of its ink, as fast as you can.
Your average night and how regular it is, by day, week, month and six months.
What it asks your iPhone for. Motion & Fitness to measure the night, Health for the sleep an Apple Watch wrote, Location to keep recording through the night, and Notifications for the two reminders. Each has a switch in Settings.