If you want to record something quickly then a smartphone is probably your best option, it means you don’t have to an extra product, carry an extra device or work out how to use something else, however, it does mean you will have a reduction in quality.
If you want to have similar ease of use, but with better recording quality, then Shure’s MV88 stereo condenser microphone is probably an awesome option for you.
It works with iOs devices, using the iPhone’s Lightning jack to provide you with the ability to record in true stereo quality, it also has a swivel head to allow you to angle the microphone’s head to the subject that you want to record, along with a foam windscreen for recording outside, carrying case and a headphone adapter cable.
Finally the microphone has matched cardioid and bidirectional catridges, with a mid-side arhitecture, 5 DSP prest modes for optimizing the EQ, compression and limiting for the sound source and environment, all in a full-metal construction.
It also has a 20 Hz to 20,000 Hz frequency response.
You can find out more about the microphone at the source link below, it is now available for around £125.