Smartphones are great for a zillion different tasks.  And developers are coming up with a ton of great guitar apps as well.  In a recent Guitar World interview, Joe Satriani even said that he demoed all the tracks for his new album on his iPhone in his hotel rooms on tour.  We've come a long way from razor blades and masking tape.

I dug around through the markets and discovered 11 of the coolest and most useful smartphone apps out there for guitarists.  Not those dopey "strum your phone and hear some midi" things.  You're playing a real guitar, so we'll concentrate on apps that will actually help your training and productivity on guitar.

At the time of this writing, many of these are only available for iPhone.  I'm sure the developers will be expanding to Android and Blackberry soon.  So be sure to check your respective markets.

Tool Kits
Ultimate Guitar Tools - This is a great tool kit from that includes a chromatic tuner with support for standard and alternate tunings, an expansive chord dictionary, and a metronome with custom presents.  $3.99 - iPhone/Android

Gibson Learn and Master Guitar - Similar to UGT, this one comes with a metronome with tap tempo, a pretty good tuner, and chord library.  The chord library here is fairly basic.  The app also includes free lesson from the Learn and Master Guitar series, which are quite good.  Free - iPhone/Android

Theory Apps
Guitar Web App - While it has a terribly boring name, this app actually has some good stuff.  It's a chord dictionary, but all explains the relationships between the chords, good substitution chords, and even appropriate chord choices for specific melody notes.  Great if you're trying to work through jazz changes or work from a fake book.  $0.99 - iPhone

Guitar Fretboard Addict - With fun games and exercises you'll not only learn the fretboard inside and out, but also ear training, sight reading, and music theory.  I paid thousands of dollars to learn that stuff in college.  You can learn it for $4.99.  iPhone

Star Scales Pro - There's quite a few chord dictionary apps out there, but very few scale dictionaries.  This one is a good scale trainer.  You'll get a ton of rock, blues, and jazz scales and learn them in multiple patterns over the whole fretboard.  Also includes options for lefty and 7-string players.  $5.99 - iPhone

Tab Apps
Ultimate Guitar Tabs - Once again from the folks, this one gives you access to every tab on their site and tools to make them useable on a small phone screen with things like auto-scroll.  The "now playing" function is very cool.  It will look up the tab for a song you're listening to, right when you get the jones to play it.  This app could be a godsend if you're taking requests at the gig.  $2.99 - iPhone/Android

Guitar Pro - Guitar Pro makes fantastic tabbing software and now you can have it on your phone too.  Display, playback, and write tabs and standard notation.  It's great for when you've got a great idea on the run and want to get down so you don't forget it.  $7.99 - iPhone/Android

For Practice
Riffmaster Pro - Ever wanted to slow down that blazing fast solo so you can cop the licks easier?  This is the go-to app for doing that.  You can slow the track down while retaining the original pitch, or not.  Your call.  Also available as a desktop program.  $4.99 - iPhone

Amplitube - effects/amps - Who ever thought you'd be able to get the sound of a 4x12 cab running through a vintage Marshall head from a phone?  Amplitube, well known for their modeling plugins, now has a phone app that includes guitar and bass modeling with recording capabilities.  11 stompboxes, 5 amps, 5 speaker cabs, and 2 different mics.  You can even import and export tracks to play with and change their tempos.  It also includes a vocal/lead guitar remover which will work as well as any of those things do, by pulling out the center channel.  To use this app you'll need an iRig interface to plug your guitar into the phone.  $39.99.  The app is $19.99.  A bit pricier than other apps, but includes a ton of stuff.  They also offer an LE version for $2.99 and a free version, each with less stuff, of course.  iPhone only.

Everyday Looper - Whether you're using looping in your live shows or just looping a practice section of music, this app will get the job done.  $5.99 - iPhone

4 Track - Some of these programming nerds need some help in the brand name department, but this is a killer little 4-track setup with a ton of cool functions.  You won't get a radio-ready recording, but it's really good for demoing song on the run.  You'll need a Guitar Jack from Sonoma Wireworks to plug your guitar into the phone.  Those run $149.  App is $5.99 - iPhone

Nothing will ever take the place of an expensive, vintage amp for a full-blown recording rig.  At least not yet.  You won't get stellar sound quality from most of these tools, but if need tools for on-the-go fun, practice, and learning, now you're all set.