PocketMeter

PocketMeter allows you to measure distances by emitting sound and measuring the time it takes for the echo to return. Just point it towards a wall or floor, touch the screen and it will show you the distance. It uses sophisticated algorithms - usually only found in active sonar or radar technology - to transform your iPhone 3G and 3GS into a modern tape measure that is always by your side and read

[sho0113]

反射音の遅延時間に基づき対象までの距離を計測.20cmから4mまでの距離を1cmほどの精度で計測することが可能

[makou]

ついでだから簡易版のImpulse Responseを記録できる仕組み備えてみてはどうか。

[gomi-box]

スピーカとマイクを使って距離を測る

[takado]

音で距離をはかるiPhoneアプリ

[youpy]

via fuba 音で距離を測る