Play! is a high-level, multi-platform PlayStation 2 emulator. Its compatibility and features are pretty far behind PCSX2, but quite a few commercial titles will run on all supported platforms, though the iOS port does not yet support input. Since Play! is high-level, it doesn't need an actual PS2 BIOS to run games. And because Play! is not a plugin-based emulator, settings and game setup are streamlined in comparison to PCSX2.
Play! is available for several platforms, both on desktop and mobile. It is the first ever PlayStation 2 emulator to run on the ARM architecture. The Android port includes support for gamepads and Android-x86. While there is an iOS port available, compatibility is low  with no input support at this time. On the desktop, Play! recently added support for Ubuntu Linux.