What was that quip from Robin Williams? āItās Godās way of telling you that youāre making too much money.ā While he was referring to cocaine it probably applies to this as well.
Iāll grant you though that this is definitely a wonderful thing for happy mutants, and I thank you for that. 
Iām going to need a smaller gauge.
I donāt usually go for expensive useless things, such as everything advertised on Boing Boing, but this sucker is really clever.
Wouldnāt amperage be more analogous to bandwidth use than pressure?
Also, what if you had the gauge measure the delta between the temperature of the routerās processor and ambient room temperature. I wonder how the results would correlate. I assume it would be less accurate and laggy but it would be a lot easier and cheaper to do.
If your speeds are in the DSL range, then you can probably find some decent old brass ammetersā¦
Ah, hereās one that gets up in the same range as Edās pressure gauge
Edit: My vote goes for an actual speedometer:
VU meters are between the cheapest meters available on the market. They can be reused for measuring both voltage and current, this way:
A microcontroller can be used for outputting analog voltage by the way of PWM. This can drive the meter directly (select the series resistor for full deflection at 5V, which corresponds to 100% duty cycle). An ATmega88/168/328 has 6 PWM outputs. It can also drive a display (LCD, graphics or text, or OLED, or whatever you please) and these outputs can be combined for interesting dashboards.
Another idea for displaying of data volumes (or other monotonously increasing or decreasing value) could be using water. Use a needle valve and a pressure sensor, for sensing hydrostatic pressure (corresponding to water column height) at the bottom of the container, control the valve to make the pressure correspond to the variable the water amount should track. A peristaltic pump can be also used, for moving fluid between two or more containers (display ones plus storage); this limits the water amount available for spillages in case of a mishap.
Edit: Read the kickstarter. Got a thought. What about using the Raspi board as a router itself? Use onboard Ethernet as one side, USB Ethernet dongle as the other? (Two or more USB dongles can be used for implementing DMZ or using two or more ISPs for redundancy.) Then the data are available for the router itself, and even some signature detection (Snort?) with corresponding alerts. Video/HDMI output then can be used for visualisation of the traffic and threats.
Sometimes I think an ohmmeter would be more representative.
Back in the days of 8-bit computers, anyone could do this for $5 in parts (less the meter; a surplus milliammeter would do). Someone - once - would need to spend an an hour or two with assembly-language to write an analog serial port driver.
Nowadays we need a separate dedicated computer because (most of) our everyday ones are so strait-jacketed and sedated. At least -they- can do whatās been lost in 20 years of āprogressā.
Even the old PCs couldāve done that. The ancient Covox adapter that hid the R-2R DAC ladder, the .mod music that played through it in glorious 8bit monoā¦ the times!
A R-2R DAC, combined with a 74HC595 shift-register, is a nice way to make analog outputs. If all you have are three wires (clock, data, latch), you can still daisychain a fairly large number of analog gauges and digital outputs for LEDs there. (Edit: With SMD resistors you can get away with just one value, and either use the 2R as two in series or the R as two in parallel. That way you buy only one kind but in higher amount, and they are amazingly cheap in bulk.)
Too bad that todayās hardware does not have exposed GPIO pins by default. The olā parallel port was pretty versatile.
With modern PCs, however, you still have a chance. Attach a microcontroller in I2C slave mode to the SMBus or any I2C bus (VGA port, HDMI port (hidden there under the alias DDC), DIMM memory sockets, they all are I2C exposed to the OS)).
A third way is using USB. Either the V-USB library on the microcontroller and software-emulate (which then is a little problematic on the host side as you have to write a service software via libusb, which you may not want to bother with), or use a USB-serial chip (my favorite is the FT232RL). Or if you want barebones functionality and just the shift registers, you can get away with FT245RL and bitbang the three wires.
This is all I can justify for my crappy DSLā¦
Heh. 
Now Iām thinking that I need something like this:
to show how much mine sucks.
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