For what device type are you inquiring whether or not they support dual WAN connections with fail over?
If you are using our Branch Router or Switch (in Layer 3 mode) platforms, then yes, these devices support WAN fail over so if the primary WAN connection drops, the device can switch over to a backup WAN connection either through Ethernet or USB 4G/3G modem.
As far as our Access Points (HiveAP 3xx Series) are concerned, they do support redundant Ethernet links. With one of these Layer 2 devices, if you configure both Ethernet interfaces in redundant mode you could connect each drop to a different switched network to provide uplink redundancy as well as link redundancy. If you do this, just make sure both switched networks can reach the HiveManager and are able to forward the VLANs on which wireless clients are being placed.
Hope this helps, if not, let me know the specifics of what you are trying to accomplish.