VPNs ('Virtual Private Networks') are a good idea to use on your mobile devices to protect your privacy when connected to a public or other untrusted wireless network.  They are designed to encrypt all of your network traffic to a third party so that no one on the network you are directly connected to get to your data.  However, you need to be careful which VPN you use.  Check out the following article regarding VPN software available in the Google Play Store that have been infiltrated by China.  Be sure to research which ones are the best to use as opposed to what pops up in the store first.

Forbes Article: New Google Warning: 280M+ Android Users At Risk As China ‘Manipulates’ Top VPNs