Appknox is described as 'Build and deploy world-class apps at scale; leave your Mobile DevSecOps to us' and is an app in the Network & Admin category. There are more than 25 alternatives to Appknox for a variety of platforms, including Windows, Linux, Mac, iPhone and Android. The best alternative is Wireshark, which is both free and Open Source. Other great apps like Appknox are tcpdump (Free, Open Source), Nethogs (Free, Open Source), netcat (Free, Open Source) and Sysdig (Free, Open Source).
Wireshark is the world's foremost network protocol analyzer. It lets you capture and interactively browse the traffic running on a computer network. It is the de facto (and often de jure) standard across many industries and educational institutions.
tcpdump is a common packet analyzer that runs under the command line. It allows the user to intercept and display TCP/IP and other packets being transmitted or received over a network to which the computer is attached.
Netcat is a featured networking utility which reads and writes data across network connections, using the TCP/IP protocol. It is designed to be a reliable "back-end" tool that can be used directly or easily driven by other programs and scripts.
Sysdig is open source, system-level exploration: capture system state and activity from a running Linux instance, then save, filter and analyze. Think of it as strace + tcpdump + lsof + awesome sauce. With a little Lua cherry on top.