Use Siri to start recording with a voice command. Just say the words and Whisper Memos begins capturing your voice.

Siri launches Whisper Memos and starts recording for you. It's great for when you want to quickly capture an idea without navigating through your phone. Just speak and your idea is saved.
Whisper Memos is free to try, and surprisingly inexpensive to use. Get it in the App Store, and start writing by talking!