What is the ruling on my work programming an application that operates a voice distributor and includes games that rely on sending text messages to win prizes?

If the program consists merely of permissible games without real prizes, then there is no objection to preparing it. However, if it involves a competition with real prizes via phone messages, the ruling on preparing it depends on the ruling of the competition. If the competition is in beneficial matters (religious or worldly) and the cost of the messages is normal, then there is no objection. But if the competition is forbidden, or yields no benefit, or the cost of the messages is higher than normal (entering into gambling), then it is not permissible to participate in it or to prepare the program, due to the Almighty's saying: "And do not cooperate in sin and aggression."