I can tune my guitars by ear and do a fair job of it. However, when I change strings I like to use my battery powered Seiko tuner to be sure. Well, today at string changing time I find that the 9V battery in it is dead and there's not one anywhere in the house.
So, I went to the Internet and found this little number, plus this one.
What did we do before we had the Internet? It's awesome.
As an added bonus, think about what we did before we had these things? To be fair I shouldn't include myself in that "we", I'm a bit of a trogdolyte when it comes to cell phones. I rarely use or carry ours.