While FS1000A and XY-MK-5V 433MHz radio modules might not be the best choice in terms of quality, or reliability or distance (although few hundred meters in open space are doable), they have one very important trait: they are extremely easy to use. No complicated wiring, no advanced programming. If you want to send some data, just connect data lines, supply voltage and write few lines of code. Super simple!
In example below, we will be sending a single 8bit number over FS1000A->XY-MK-5V line with a help of VirtualWire library.
Please remember, without antennas and in radio-noise rich environment, range might be limited. Very, very limited. Even to just a few centimeters. So keep that in mind!