Always-on point-to-point audio link over the internet?

[bbee]

Hi,
I'd like to set up an always-on two-way audio connection over the net. One of the endpoints is a dualcore device with GBs of RAM and gentoo linux, the other is a rather limited device:

- It has a 486-class CPU at 133 MHz and 64M of RAM
- Sound is prorably going to be a simple PCI soundcard
- The downlink is capped at 1GB/month, works out to 3 kbit/sec. Uplink is unlimited. Latency is good (<100ms).
- Dynamic IP that changes often.
- OS will probably be OpenBSD, linux is an option

Does anyone have any experience with a setup like this or can reccomend some software? Asterisk and the like is probably complete overkill. Ideally it would be a simple crossplatform client/server application, with the server listening on a fixed IP. It should support things like sound level detection to stop packets going out if there is no sound (to preserve bandwidth), as well as echo cancellation etc. The requirements of the audio codec need to be pretty low due to the very slow CPU having to decode a stream. However the stream it sends back might as well be uncompressed since the uplink is unmetered (128 kbit/s).

Any takers?