Take a look at:
Honda Fit Accessories - Genuine 2009 Honda Fit Accessories Shipped at Discount Prices
for your 09. Honda sells a kit to do this, with a much cleaner installation IMO. (no offense to you TFB)

I'm planning on doing this and maybe adding another stip of leds.

 

Yeah, but thats too complicated for me.

Also, the light is very dim with Honda's.

 

I have an 09 Honda Fit, and I just installed blue LED floor lighting. It looks great in my car especially at night. I have mine completely hidden out of view under the dash, and I have mine hardwired into the fuse box that way I have no exposed wires anywhere. I debated on adding a switch to the lights but decided against it because I don't want to forget to turn them off and drain the battery. I have my wires hardwired into the daytime running lights, so the lights will only turn on when the car is turned on. I will post pictures soon if anybody is interested.

 

I installed blue cold cathodes on my last vehicle, a 2000 Grand Voyager SE. Ignoring how unnecessarily badass -- er, unique -- it made my vehicle look, I really did work to make the lighting permanent.

The power outlet (cigarette lighter) was the perfect choice as a power source since it was enabled and disabled with the ignition. Basically, I didn't want the lights to draw power unless I was in the car. With the car and ignition off, I removed the stereo bezel to access the back of the lighter outlet and cut the red power wire from the outlet back. I allowed enough slack on the cut ends to eventually screw cap them back together and later zip tie for safety.

Very simply, I purchased standard molex cold cathodes (like the ones you put in modded computers) from newegg.com for around $8, and cut off the molex connection (plastic four-pin female connector) before the inverter. This gives you two wires, typically a red and a black wire. For safety reasons, you should run a 5-amp inline fuse from the red wire to the lighter outlet source along with the now disconnected outlet. These can be easily screw capped together. I like adding a healthy dab of hot glue inside the cap to really make things stay in place. Then I zip tie everything together.

The black wire from the cathode inverter needs to run to a grounded bolt on the car frame. Any non-painted bolt near the car's firewall will do. Here's the deal though: You can run some length of low power speaker wire to the cathode's black and red connections. This will allow you to extend the range of the cathodes so long as you do this before the inverter and inline fuse and NOT AFTER. For each set of cathodes, an inverter (typically a little blue plastic box) needs to be close by.

As such, in my van, I had an inverter in the front of the car that powered the driver and passenger sear lights. Then a five-foot span of speaker cable ran from the front lighter outlet to the second row seating inverter. Each run had one inline fuse.

With ALL of this said, I had the cathodes in place, no problems for three full years until I recently sold the vehicle. Since then, I've installed cathodes in my house as ambient lighting as well. Really, I love cathodes.

Now I own a new Fit.

I have to admit, while doing all of the work myself took under an hour, I think Honda's ambient lighting kit is the way to go for the Fit. It integrates with your backlighting levels on the gauges and has conveniently matching power switch. This is just really slick and impossibly brainless.

 

I will post pics soon I put the lights in too when I first got my fit but I dd it so they ran all the time I got an cig plug extenders and splitter it has 3 rifle switches built it with hi intensify ble LEDs and I got a plug with the wingnuts at radio shack I just put the ends in the plug and hit the togle switch and walahhh lol trust me it's the best thing I have done to my car since 99% of my driving is for at night the lights help