Nick Poole, a technologist for SparkFun Electronics, built this beautiful Arduino-powered rainbow box:

Recently, I had the opportunity to see Phil Lapsley talk about his book “Exploding the Phone,” a history of phone phreaking. When I found out that he was coming to give the talk, I was reminded of a project that I had been wanting to undertake for some time now but had never gotten around to. In an afternoon, I turned an Arduino, a keypad and a buzzer into a “rainbow box,” which emulates five different phone phreaking tone generators. I gave it a little bit of retro appeal as well with a heavy aluminum enclosure, lots of masking tape and some 2600 Magazine stickers that I printed on the xerox.

I got to see a real BlueBox from the 70s, which Phil brought with him. It was awesome. A true hack.