The Clear Spot 4G+ has the added functionality of being able to switch to the EVDO 3G network when 4G isn't available, and it supports up to five Wi-Fi devices. It can be bought for $225 or leased for $6 per month. The 4G+ S Series USB modem also features the ability to jump between 3G and 4G networks, and it's compatible with both OS X and Windows-based machines. It costs $115 or $6 each month.
All three devices are up for preorder with a July release window. They can be coupled with unlimited data plans that start as low as $30 (home) or $40 (mobile) in most markets, which is currently limited to a handful of large US cities.