Pictured below is an electronic display module we have been testing out recently.
Available at under £2 including delivery (see here: buy TM1638 module), the pictured device offers 8 LEDs, 8 input buttons, and 8 7-segment LED display digits which can be fully controlled with just 3 pins from your Arduino (or other microcontroller unit).
We are looking at these to offer alternatives to the LCDs (liquid crystal displays) we currently use in our solar water heating pump controllers and low voltage disconnects in particular, since the two sets of 4 digits on these modules’ displays can show a voltage to two decimal places plus other information, or two temperature sensors readings also to two decimal places simultaneously. Seven segment displays are much more readable from a distance, and the availability of 8 LEDs and 8 user input buttons opens up many new possibilities.
Initial results of testing have been very positive. If you are interested in getting started with these modules and Arduino, an excellent starting off point is this excellent article: Arduino and TM1638 LED Display Modules from the Australian site tronixstuff.com. All you need is an Arduino board, the Arduino IDE (the software required to programme your Arduino), and the TM1638 library available here.