Hello All, I'm the developer of iTanpura and the soon-to-be-released iLehra. Came across this post and thought I'd respond as well. Thanks to the members that recommended iTanpura (think I know who you are). Just a couple of points:
1) iTanpura has better quality and features than anything on the market. I would really challenge anyone to find a better-sounding electronic tanpura, heck it sounds better than most real tanpuras because of the quality of the tanpuras used to make the sample recordings. As a practicing musician, quality was my foremost concern - this is something I can use for any of my concerts without any concerns. Especially since using this with a battery-operated speaker dock gives me 10+ hours of wireless sound! And with every version I've added the most requested features including presets - this lets you pre-tune for all the raags you're planning to sing in a concert and then quickly switch to the next one. Intend to keep adding features as well. And unlike the physical models, all users get all updates for free.
2) Regarding the cost, this is certainly subjective and I respect the opinions of people who may find this expensive. However there is a reason its priced where it is. The potential market for this cannot compare to say a guitar tuner or chords app. The number of people who are practicing Indian classical music and have an iPhone or iPod Touch is a very small fraction, so there is no way I can price this app the same way. However if you look at what dedicated units cost (the Radel unit is about $100) this is way cheaper, and has the added advantage of extra mobility. For example, just plug it in to your car stereo and you have the ability to practice on your long commute. As a data point, there was another similar iPhone app a few months ago called iTabla that cost $150 (its since been yanked from the app store since the developer got cute and advertised it as free even though you needed to pay $150 to get an activation code).
Anyway, having got that off my chest, if any of you have ideas or feedback for this or other similar apps do let me know.
-Prasad Upasani
http://upasani.org