There are a variety of mobile apps that work well in conjunction with SDF and can enhance your experience here. We will highlight open source/free software for the most part, only adding 'pay' software on request or when there is no other useful alternative.
JuiceSSH - SSH Client
Connectbot - Open source SSH/telnet client
K-9 Mail - Open source email client for advanced users
Xabber - Free Jabber/XMPP client
Overbite - Open source Gopher browser
Tusky - Open source Mastodon client
BBSSH - Free, open source SSH/telnet client