I've built something similar using point-to-point Wifi gear. It kinda sucks having to align to line up two antennae but you get much better range.

I am using Ubiquiti Networks (http://www.ubnt.com/) equipment used in long haul Wireless ISPs. This equipment is inexpensive and uses standard technology: Power-Over-Ethernet (POE), Wifi, so it's easy to tweak.

I'm using a 9 amp-hour battery and current draw is ~0.6 amps so that comes out 10 hours or so. It would be trivial to tack on a Solar panel or bigger battery. The charge controller takes POE as an input so it's easy to recharge the battery.

Here are a couple pics:

Shows the camera side of the setup: http://imgur.com/PvjuFRJ

Shows two .30 cal shots my tripod took and kept standing. :-) http://imgur.com/aa37kzt

The price tag for my setup came out to $438, here is the parts list:

2 x AmazonBasics 60-Inch Lightweight Tripod with Bag http://www.amazon.com/AmazonBasics-60-Inch-Lightweight-Tripod-Bag/dp/B005KP473Q/ref=sr_1_3?ie=UTF8&qid=1403996810&sr=8-3&keywords=tripod $48

POE/Solar Dual Input 12V Battery Charge Control (TP-SCPOE-1224) http://www.ispsupplies.com/brands/Charge-Controllers/Tycon-Power-TP-SCPOE-1224.html $52

12V 9AH AGM SLA Battery (TPBAT12-9) http://www.ispsupplies.com/brands/Batteries/Tycon-Power-TPBAT12-9.html $26

Power extender over ethernet for Foscam (WS-POE-5v-10w) http://www.amazon.com/gp/product/B00DAMKQWW/ref=wms_ohs_product?ie=UTF8&psc=1 $12

Foscam FI8905W Outdoor Wireless/Wired IP Camera http://www.amazon.com/gp/product/B003YUEF0E/ref=wms_ohs_product?ie=UTF8&psc=1 $92

Ubiquiti NanoStation M2 http://www.amazon.com/Ubiquiti-NSM2-US-NanoStation-M2/dp/B004EFH6L8/ref=sr_1_1?ie=UTF8&qid=1403997019&sr=8-1&keywords=nsm2 $86

24V 1A 24W Wall Plug Passive POE Inserter (TP-POE-24-WP) http://www.ispsupplies.com/brands/POE-Sources/Tycon-Power-TP-POE-24-WP.html $12

3 x 10FT 24AWG Cat6A 500MHz STP Ethernet Bare Copper Network Cable - Blue http://www.monoprice.com/Product?c_id=102&cp_id=10232&cs_id=1023216&p_id=5902&seq=1&format=2 $15

MTM Ammo Can (Forest Green) http://www.amazon.com/gp/product/B003ISKM9K/ref=oh_details_o00_s01_i00?ie=UTF8&psc=1 $16

DC Inline Watt Meter and Power Analyzer, Powerpole Ends http://www.powerwerx.com/digital-meters/dc-inline-watt-meter-power-analyzer-powerpoles.html $60

Revo 5" Hand Grip for HDSLRs and Video Cameras (Black) - Used for mast to strap Wifi antenna to http://www.bhphotovideo.com/c/product/930248-REG/revo_vb_120b_5_hand_grip_for.html $14

1" Schedule 40 PVC Pipe Hardware Store $5