It would probably be best to use a microcontroller instead of a full cpu. I really like the Particle Photon. It costs $20 and is a joy to work with. It barely n

It would probably be best to use a microcontroller instead of a full cpu. I really like the Particle Photon. It costs $20 and is a joy to work with. It barely needs any power in sleep mode, and you can set it to wake up at scheduled intervals. Depending on the battery you use, a month of battery life shouldn't be an issue if it sleeps most of the time. There are other microcontrollers with Wifi and similar capabilities that are even cheaper, like the ESP8266 at around $5, but I haven't worked with those before. EDIT: I just saw you want it to wake up every five seconds --- in that case sleep won't help much and you'll need a big battery for a month of use, since wakeup and scanning for networks takes a few seconds. Waking up less often (eg. every 15min) would be more feasible, but it really depends on your intended use.