You can start by asking yourself the following question: What application would you like to see on your mobile??
Then you can look for inspiration at other places: there have been two Android developer challenges(ADC) you can take a look at the award-winning applications and the various submissions to get an idea of what the competition is like and what apps already exist. You may also want to check out creative firstname.lastname@example.org for ideas that others think are cool.
hi,Amit 'm happy to hear that you wanna work in your vacation.
For more ideas on Apps , have a look at Apple App Store (just to get feel of smart phone apps) !
Go through what kind of apps are there for Smart phones..
good luck 4 project ! lets us know your project (if you wish)....