@325xi,
the create-a-serial device process (in 1.0.944) looks something like the following (all examples translated to your IP space for realism, Please DON’T click the links!!)
[tt]http://192.168.1.131:49451/data_request?id=lu_action&serviceId=urn:micasaverde-com:serviceId:HomeAutomationGateway1&action=CreateDevice&Description=Serial_Portlist_IP192_168_1_90&Invisible=1&deviceType=micasaverde-com:serialportroot&internalID=IP192_168_1_90&IpAddress=192.168.1.90[/tt]
which returns something like:
[tt]<?xml version="1.0"?>
<u:CreateDeviceResponse xmlns:u=“urn:micasaverde-com:serviceId:HomeAutomationGateway1”>
228
</u:CreateDeviceResponse>
[/tt]
where “[tt]228[/tt]” is the Parent device Id that will contain the Serial Port.
You then create the Child Serial device, which looks something like:
[tt]http://192.168.1.131:49451/data_request?id=lu_action&serviceId=urn:micasaverde-com:serviceId:HomeAutomationGateway1&action=ProcessChildDevices&DeviceNumParent=228&DeviceList=ID=Remote90 Embedded=1 UpnpDevFilename=D_SerialPort1.xml DeviceType=urn:micasaverde-org:device:SerialPort:1 Description=My%20Remote%20Device Argument,urn:micasaverde-com:serviceId:HaDevice1,Protocol=RS232[/tt]
passing in the DeviceNum that was previously returned ([tt]228[/tt] in my case, but will be different in each use). There’s something a little “off” in the above, as it’s not returning the Child Device Id (which I’d expect)
You then do something like:
[tt]http://192.168.1.131:49451/data_request?id=lu_reload[/tt]
Most of the above is by trial and error, so there are likely problems. Once I wiki-ize this, we can collaboratively “correct” the descriptions over time.
The above will create the stubs in Vera, so that you have a [single] Serial Port hanging beneath the area:
[i]Luup Plugins --> Serial Port Configuration[/i]
You can then set the “IP:”, “Port:” and “Used by Device:” attributes on the Serial Port in Vera’s config, Save, and Vera will connect to the Remote IP/Port combo.
In my case, I’ve hard-coded a [tt]ser2net.conf[/tt] file on the “remote” (ASUS) end, and I’m not pulling down any of the User-specified config data from Vera.
Since this is experimental, and I don’t have the source to [tt]serproxy[/tt], no warranties about what else it might do 
UPDATE: Jan 28 2010
The funky manual URL steps I’ve listed above to register a remote IP-based Serial Port can be replaced by the work-around Plugin code in this thread:
http://forum.micasaverde.com/index.php?topic=2989.msg12655#msg12655
This should make it a little easier to “register” these ports, at least until the Vera-native solution is in place.
Updating this thread in case folks search…