I have never used an oscilloscope since I am not into board repair but I have seen the term thrown around here a lot, could this be used for older arcade game repair purposes?
http://www.thinkgeek.com/electronics/cell-phone/e94d/
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You don't want that, at least not for that price. If it was $40 and you already had an iPad, perhaps, but as it stands it's $299 for a single channel, VERY low bandwidth scope (5Mhz is NOTHING) with 4 bits of digital added. The Rigol 1052E mentioned elsewhere (even if you don't hack it!) is $399 (
http://www.tequipment.net/RigolDS1052E.html) for a 2 channel scope that does 50Mhz and has it's own display. MUCH better deal.
Heck, and if you want a scope that doesn't have it's own display, the MSO-19 from Link Instruments (
http://www.linkinstruments.com/mso19.htm) has 1 channel of 60 Mhz bandwidth scope and also 8 input logic analysis. That's even cheaper than the iPad thing!
So, basically, unless you need to look cool by using your iPad as a scope, no, that's not really something you want to buy.