Everyone knows Riverbed as a WAN acceleration vendor. Earlier this year they announced something called "Granite" which lets you run VMs on an appliance in a remote branch office while keeping the disk images in the central office. The remote VM accesses the disk blocks across the WAN as needed, and the appliance handles caching, replication, and keeping everything in sync.
At VMworld last month, Riverbed announced that they're working out the details of making this granite technology apply to VDI workloads. (So you have your VDI VMs running locally at the remote branch, but the disk images they're running on are housed in the central location.) In some ways it's like Citrix Provisioning Server over the WAN. The idea is that you get "custody" of your data in the datacenter while leveraging the power of local branch-level computing power to run the VMs.
Right now this is just a tech preview, but they're working on integrating it with the connection brokers to provide more smart routing and spinning up of desktops.
Here's a video with Riverbed's Eric Carter explaining how Granite applies to VDI: