Thomass1237:
The thing I'm wondering is how I can possibly send 500-1000 bottles with gps cheap.
this project raises a lot of questions
first, please define cheap ...
what is your budget?
where do you want to drop the bottles?
sea?ocean?river?
What communication did you have in mind for the feedback?
Do you want interactive or real time data? (expensive -> GSM option??)
Or do you want to store gps data on a flash card and catch the bottles after a week?