i really want to do this too....
been looking at tablets seen this : http://yamaytech.en.alibaba.com/product ... et_pc.html
think it has all the right specs, but i can't find one for sale anywhere or even this one with less specs but woudl do the job:
http://fastgo.en.alibaba.com/product/52 ... ction.html
so thinking of a dropad a8t, but costing a bit more...http://www.ebay.co.uk/itm/Dropad-A8T-Ul ... 871wt_1163
but would really like one around £70, just to keep costs down..but that's just dreaming to find one with , 7in,gps,bluetooth,1280x600,1ghz up,1gb ram.
The archos 70 looks alright, i have a arnova(archos) 10g2 with gingercomb(custom rom) on it, they are good kit. Maybe go for one of them.
a rough guide for doing this would be great as others have stated.