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    <p>There is a <a href="http://mail.python.org/pipermail/python-list/2009-April/thread.html#177175" rel="nofollow noreferrer">very similar thread</a> on a Python mailinglist that mentions Windows <a href="http://en.wikipedia.org/wiki/COM_port_redirector#Virtual_Serial_Port" rel="nofollow noreferrer">virtual COM ports</a> and discusses Unix's pseudo-tty capabilities. If the app(s) you want to use let you type in a specific tty device file, this may be the easiest route. (Short of asking the authors to provide a plugin API for what you're trying to do, or buying yourself a <a href="http://www.semsons.com/amabg108blgp.html" rel="nofollow noreferrer">$20 bluetooth GPS mouse</a>.)</p> <p>Are you using OS X?</p> <p>There is a project <a href="http://code.google.com/p/macosxvirtualserialport/" rel="nofollow noreferrer">macosxvirtualserialport</a> on Google code that provides a graphical wrapper around some of the features of a utility called <a href="http://www.dest-unreach.org/socat/" rel="nofollow noreferrer">socat</a>. I'd recommend taking a look at socat if you see potential in the pseudo-tty route. I believe you could use socat to link a pipe from a Python program to a pseudo-tty.</p> <p>Most native Mac apps will be querying IOServiceMatching for a device with kIOSerialBSDRS232Type, and I doubt that a pseudo-tty will show up as an IOKit service.</p> <p>In this case, unless you can find a project that has already implemented such a thing, you will need to implement a driver as described in this <a href="http://lists.apple.com/archives/Darwin-kernel/2006/Feb/msg00090.html" rel="nofollow noreferrer">How to create virtual COM port</a> thread. If you're going to the trouble of create a device driver, you would want to base it on IOKit because of that likely IOServiceMatching query. You can find the Apple16X50Serial project mentioned in that post at the top of <a href="http://opensource.apple.com/release/mac-os-x-1061/" rel="nofollow noreferrer">Apple's open source code list</a> (go to the <a href="http://opensource.apple.com" rel="nofollow noreferrer">main page</a> and pick an older OS release if you want to target something pre-10.6). </p> <p>If your app is most useful with realtime data (e.g. the RouteBuddy app mentioned in the Python mailinglist thread <a href="http://www.routebuddy.com/routebuddy/devices/index.html" rel="nofollow noreferrer">can log current positions</a>) then you will want to fetch updates from your web sources (hopefully they support long-polling) and convert them to basic <a href="http://www.sparkfun.com/datasheets/GPS/NMEA%20Reference%20Manual-Rev2.1-Dec07.pdf" rel="nofollow noreferrer">NMEA</a> RMC sentences. You do not want to do this from inside your driver code. Instead, divide your work up into kernel-land and user-land pieces that can communicate, and put as little of the code as possible into the kernel part.</p> <p>If you want to let apps both read and write to these web services, your best bet would probably be to simulate a Garmin device. Garmin has more-or-less documented their protocol in the IntfSpec.pdf file included with their <a href="http://garmin.com/support/commProtocol.html" rel="nofollow noreferrer">Device Interface SDK</a>. Again, you'd want to split as much as you could into user-space code.</p> <p>I was unable to find a project or utility that implements the kernel side of an IOKit-based virtual serial interface, but I'd be surprised if there wasn't one hiding somewhere out there. Unfortunately, most of the answers I found to that question were like this, with the developer being told to get busy <a href="http://developer.apple.com/Mac/library/documentation/Darwin/Conceptual/KEXTConcept/KEXTConceptAbout/about_kexts.html" rel="nofollow noreferrer">writing a kext</a>.</p>
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    1. COSome really useful stuff there, thanks. I am indeed using OSX (added detail to original question).
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    2. COA $20 gps mouse is a good point (and a great 'poor-mans gps!), but my overall aim is to provide a virtual GPS 'data stream' from non-GPS web API's.
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    3. COAs an aside, I really hadn't realised how cheap GPS dongles are now: http://www.amazon.co.uk/s/ref=nb_ss_0_6?url=search-alias%3Daps&field-keywords=gps+receiver
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