Hello, thank you for the opportunity to bid on your project!
I've developed several BLE devices over the past few years, ranging from ultra low power air quality monitoring to a tiny BLE camera module. Since you haven't specified a platform, I would like to recommend the Nordic Semiconductor nRF51822; they have several inexpensive development boards to help get us started quickly.
Your budget is reasonable for the physical hardware costs for a prototype or two, but as a design budget it is low. I'm submitting my bid as a list of milestones which I hope will help to address the design and ensure that I will be able to deliver a prototype that meets your requirements. I've found that oftentimes on Freelancer there is a bit of front-end iterative work required to clearly define the project requirements in order to provide an accurate and realistic bid. I hope that you agree.
In addition to the milestone delivery strategy, I host a project management site which I use internally and offer access to any client; it provides very good insight into the development progress and allows you to see the day-to-day development process.
If you have any questions about the bid please feel free to contact me. I'm looking forward to working with you.
Regards,
Andrew