Modifications
Old Nokia 3310s (which are often available for a small fraction of their original price at charity shops and car boot sales) are frequently sought out by hobbyists for their screens. These are graphical LCDs with a resolution of 84x48, and include a Philips PCD8544 controller which is easily controlled using an SPI bus.
The mobile phone features an MBus and FBus.
In addition to the use of the displays, other electronics hobbyists have also used the 3310's casing to contain WiFi spectrum analyzers and other useful devices. Normally the phone does not work as a phone afterwards but one workaround is the use of two 4016/4066 quad bilateral switch IC's to switch between one of several modes.
Another worthwhile hack is to enable three colour backlighting by sequentially driving the screen with red and blue LEDs at above the visual fusion frequency. White is enabled by driving both frames with the same data. This technique was used on older JVC camcorders so they could use a B/W screen yet still display colour.
In theory the 3310 can be retrofitted with a camera by using the microphone input as a data port, in much the same way that SSTV works. As the maximum frequency is typically 8 kHz it would take about 500ms to transfer one frame to the display so a microcontroller would be needed.
A hack suggested in the wake of the Fukushima Daiichi nuclear disaster was to modify phones to be used as Geiger counters. Some types of Geiger tubes can be modified by the use of a strong permanent magnet to increase sensitivity so that a SBM-10 Russian surplus tube can be used and connected via an optoisolator to the microphone input.
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