As anothe answer said there is nothing illegal about writing such an app, restrictions may well apply to running it, and particularly to charging money or accepting winnings from it. There are lots of apps that can earn you money just for using them.
https://debate.socialism.nl/forum/showthread.php?tid=282684 http://www.lada-xray.net/showthread.php?p=318404#post318404 http://60.250.226.63/ipkb/viewtopic.php?f=41&t=1935488 http://frmklas.com.tr/threads/best-roulette-strategie-online-casino-jacks.31177/ http://mirosovak.edoras.cz/viewtopic.php?f=3&t=542706 https://www.ww2.site/forum/viewtopic.php?t=99936 https://www.ww2.site/forum/viewtopic.php?t=94151 http://forum.fretky.cz/jak-ji-naucit-na-zachod-fretci-toaleta-a-vse-kolem/norske-pokersider-beste-norske-casino-t191822.html https://www.ww2.site/forum/viewtopic.php?t=115195 https://www.ww2.site/forum/viewtopic.php?t=399513 https://www.ww2.site/forum/viewtopic.php?t=275519 https://debate.socialism.nl/forum/showthread.php?tid=333377 https://67farms.st/viewtopic.php?t=19144 https://phantom.everburninglight.org/archbbs/viewtopic.php?pid=696526#p696526