Waterproof beeping device

[technoyos]

Hello,
I'm a real Noob to this electronics thing (but I find it fascinating..). Anyway, I want to try to build a device that beeps. The duration and pitch of the beep is fixed, but the frequency should be variable, depending on user input. The whole device should be as small as possible and water proof.
I would prefer to be able to control the beep frequency remotely - perhaps from a mobile phone or from something like a remote controller. The beeping unit should be kept simple as possible.
Any ideas on how I can achieve this using your parts?

Thanks,
Yossi

[adafruit_support_bill]

Lots of possibilities there:

The whole device should be as small as possible and water proof.

Waterproof as in submersible, or just weatherproof?

I would prefer to be able to control the beep frequency remotely

What kind of range? Does it need to go around corners, or is line-of-sight acceptable?

[technoyos]

Waterproof means it might be used in swimming (under a swimming cap, for example), or in rainy conditions, but not in diving, for example.
Also, a line of sight is sufficient for my purpose.
I thought of 2 possible ways - a mobile phone generates the beeps (easy to do with a simple application) and the beeps are sent (perhaps using a Bluetooth audio module) to the beeping device, or the device contains a remotely controlled (again, Bluetooth?) 555 timer + .
Any other suggestions will be very helpful.

[adafruit_support_bill]

For line-of-sight, IR would probably give you the most compact solution using off-the-shelf parts. You could pair one of these with an Arduino Micro. Our Piezo beepers are not waterproof, but you can get a waterproof one from Radio Shack. The rest of the electronics would fit in a pill-bottle, or could be shrink-wrapped for the most compact waterproof package.

A low-power radio such as an XBee would be another option, but bulkier. There are some pretty small WiFi or Bluetooth modules, but most need to be connected to a USB host.