I did a search on here for "tuners" and found basically a minimal amount of discussion so I thought I'd share this app from my Android phone. (I know a lot have the iPhone) and of course a contact tuner is far more accurate and I realize the digital microphone translation is questionable on any tuner but this gets a new student up and running without breaking strings needlessly.

I'ts called G Strings in the droid market and you can download the "FREE" version or pay $3.00 for the "PAID" version. I use the free one, it's fine. (Probably out of tune since it's free, LOL) 

The app has a lot of settings to use, capable of tuning many instruments, can play the tone for the note or 'auto tune' the notes you're playing. I find it very easy to use, and it's hands free in the auto setting.

When you get real close to the proper freq it changes color to show you what range you're in. You can change the background color to suit your taste or mood and all in all it's a very nice tuner for the price.

Just a thought for those beginners starting out without much cash for accessories and you'll most likely always have THIS tuner with you where you go.