Just been playing (with a fair bit of cut/pasting) with some HTML/CSS and have ending up with the following "App" for iPhone (and likely to work on Android, but not got one to test it with).
C5 Speedo
"complete with Sinclair font"
Simple to install (he says....
), no Apps to download, just visit the following webpage with your iPhone:
http://c5speedo.cm7.ch/0.1/then with the phone in portrait mode tap the "share" arrow in the middle of the screen, then click "add to home screen", like so:
This adds a icon to your phone, which when clicked opens the "app". The "app" (or Safari, if you don't want to install) will then ask that it will want access to your location, you will need to give this, as the html needs to use the GPS on the phone to get the speed.
Also to note is that the files are all stored "offline" so no data connection should be needed when in use. It is also worth noting that, like all GPS "apps" it will use the battery a little more than normal, so please bare that in mind.
0.1 version, so I'm sure there maybe many improvements, but let me know if you have any handy feedback - The source code can be found here should anyone be interested:
http://c5speedo.cm7.ch/0.1/c5speedo.zipThat's all for now - next step - best way for mounting the iPhone on the C5