And you can always use a tool like webmin to manage RPI(and any Linux) via browser, including openvpn service. There are plenty of detailed guides on how to install it on RPI, the gist is:
apt-get install -y perl libnet-ssleay-perl openssl libauthen-pam-perl libpam-runtime libio-pty-perl apt-show-versions python wget http://prdownloads.sourceforge.net/webadmin/webmin_1.660_all.deb dpkg --install webmin_1.660_all.deb
PS: It should be easy to write a cgi script that wraps around "service openvpn status", "service openvpn start" and "service openvpn stop" in any language, especially if you don't care much about permissions "at home"