What mobile device should I use to record swims?

1. Supported operation systems are
– Android 6.0 and greater.
– iOS 8 and greater.
2. Supported bluetooth chipsets:
– Other than Samsung Exynos
3. Bluetooth version
– Version 4.0 and 4.2.
– version 4.2 recommended, because it give much faster transfer speed than 4.0.