I charge up my cell phone and use it as an alarm clock. However, don't turn it on unless you have set up an international calling plan with your carrier. Voice mails received can be charged at the full $2.49 per minute rate! I turn it on and set the alarm just before I go to bed.
I don't use a bungie cord - too dangerous. I use a 10" x 1" round dowel rod to wedge into the area between the door hinges and it works perfectly and takes up almost no space.
I keep a small suitcase of travel things at home with the dowel rod, multi-plugs, handwipe singles, etc and just grab what I need when I am ready to pack for a cruise.
Been there - done that:
2005 Holiday, Sensation, Conquest,
2006 Conquest, Celebration, Holiday,
2007 Freedom Grand Med, Holiday
2008 Fantasy & Sensation,
2009 Fantasy, Holiday & Dream Grand Med
2010 Fantasy and B2B Elation
2011 Monarch of the Seas
2012 Booked - Breeze from Barcelona 12 days