Google Nexus 7 tablet
 

This 7" tablet is awesome. This is by far the best mobile device I have used so far, Palm, Apple, Blackberry, Windows, Android all included. If you already have unlimited data on your smartphone using a free WiFi tether app, a piece of cake with Android 4.0 and higher, then this $230 tablet is a no-brainer. Couple it with the $35 Google Chromecast HDMI plug for you TV at home and this is a powerful combination for less than $270. I'm so impressed with this tablet that I'm not going to bother upgrading my phone. With my LG Tone ($50 eBay) Bluetooth headphones I can make outbound calls on the tablet when its tethered to the phone. Incoming calls are answered with the headphones, so no need to get out the phone.
If battery drain is an issue I simply connect the phone to a super thin external battery purchased on Amazon for $40. Anker make some that you can plug multiple devices into and have 10,000 mAh's or 8x's the capacity of an IPhone battery. Right now I'm using the I/O Magic battery from Staples at 4,400 mAh. Between that, and my Motorola phone's 3,400 mAh battery I've got mobile 4G LTE /WiFi that can run all day without carrying any heavy gear.
And more importantly without any extra monthly charges since Android allows for free WiFi tether without having to jailbreak or root. This alone has saved me enough to buy a phone outright. Also, this is easily the best looking screen available on any device bigger than the Iphone and a significant upgrade over the mini iPad screen which is priced $100 more.
You can check out the tablet at Staples, BestBuy or Sam's but I would make the actual purchase on Google's site. The return policy for many of those stores suck especially BestBuy's.