Your excuse for playing out of tune, besides from not being able to tune your guitar, is that guitars grow and expand from the humidity. Some smart dudes invented the N-Tune gadget that attaches to a guitar without drilling, so you can always tune your guitar on the spot.
The idea was interesting enough to get $1.1million in funding from venture capitalists to start producing and marketing the N-Tune, as it is called. They already have orders in for 10,000 units. It's a very good idea.