You can record pretty good audio on an iPhone or iPad, but if you’re a more serious vocalist (or podcaster), the audio features will eventually feel too restrictive.  

Check out the VocaLive app ($20 on Apple). It’s gives you 12 effects including Pitch Fix, Choir, Morph, Reverb, Phazer, and Delay. You can also import songs to sing along with, or remove the vocals from a track and insert your own. A single-track recorder is included and they offer an add-on four-track recorder for $5.  There’s a lite version that’s free with, obviously, less bells and whistles.

And while you’re upgrading your vocal recording studio, take a look at the iRig Mic ($60 on IKMultimedia.com). The iRig is a condenser mic that plugs into an iPhone or iPad and delivers way better sound than the internal mic.