The days of mobile recordings being limited to grainy video and maybe-understandable audio are over. High quality cameras in our phones and tablets have become as good (or better in many cases) as stand-alone cameras - for both video AND photos.
But unfortunately we haven't seen nearly as much improvement in the on-board microphones in these devices. But a market has emerged in ways to attach microphones (either the ones you already have, or those designed to attach directly) to our mobile devices. Whether you're using an Android phone, an iPhone, or even a tablet, using an external microphone can drastically improve the quality of your recordings.
You may not want to try and record vocals for a studio album through your iPad (although this is becoming VERY possible with every month that passes, it seems), but recording the audio of an interview for later publication is much more within reach. Heck, forget about "later." Live streaming using microphones plugged into my iPhone (using an interface called a Soundblaster K3+, which I reviewed here) makes us sound MUCH more professional than using the built-in mic.
Take a look at what external mics there are and what it will take to get them working with your device. The benefit they offer far exceeds their cost.
Here is a roundup of the 10 best microphones for mobile devices from MicReviews.