I like to play at night, lying in bed. To do this, I keep a compact MIDI keyboard right on the bed under the wall. This block allows you to connect to the iPhone via Bluetooth and supply power to the keyboard.
Works reliably, without failures and without delay of a sound.
Maybe someone does not know: you need to connect to the iPhone through GarageBand.
Disadvantage: the iPhone does not remember the connection.
Conclusion: reliable and very convenient thing.
Sorry for my English.