OpenVPN for Android
You make your life and that of your users easier if you embed the certificates into the .ovpn file. You or the users can mail the .ovpn as a attachment to the phone and directly import and use it. Also downloading and importing the file works. The MIME Type should be application/x-openvpn-profile.
Inline files are supported since OpenVPN 2.1rc1 and documented in the OpenVPN 2.3 man page (under INLINE FILE SUPPORT)
(Using inline certifaces can also make your life on non-Android platforms easier since you only have one file.)
For example ca mycafile.pem becomes
<ca>
-----BEGIN CERTIFICATE-----
MIIHPTCCBSWgAwIBAgIBADANBgkqhkiG9w0BAQQFADB5MRAwDgYDVQQKEwdSb290
[...]
-----END CERTIFICATE-----
</ca>
Please note that OpenVPN used by this project is under GPLv2.
https://play.google.com/store/apps/details?id=com.lutech.freevpn
Please read the doc/README before asking questions or starting development.